Allan George Bromley (1947-2002) was an Australian historian of computing in the Computer Science Department at the University of Sydney. Internationally recognised as a leading authority on early computing devices—including the Antikythera Mechanism and Charles Babbage's Difference Engine—he was also one of the world's most dedicated collectors of calculating instruments. He displayed a small selection of his collection in the rear foyer of the Department of Computer Science (Fig. 1), while the vast majority was housed in his home, where his "assortment of analog computers [...] inspire[d] awe among fellow collectors and museum curators" (Sydney Morning Herald, 1999). His collection encompassed mathematical instruments, slide rules, mechanical and electronic calculators, electronic analogue computers, computer components, and related ephemera. Bromley began collecting calculators in 1977. Over the following two decades, his collection expanded to more than 3,000 objects and 10,000 books (pers. comm. Anne Bromley). It originated with approximately 500 slide rules, most acquired from London's antique markets during his time at the Science Museum. Over the years, it grew into the largest privately owned slide-rule collection in the Southern Hemisphere (Sydney Morning Herald, 1999). As both a collector and historian, Bromley reflected on the practice of collecting in his 1981 article Collectorabilia Dr. Allan Bromley, which may be the earliest published account devoted to the private collecting of computers and computer-related artefacts. Correspondence preserved in his personal papers provides further insight into the acquisition of rare analogue computers and other calculating devices. In the final years of his life, Bromley donated many of his most significant artefacts to the Australian Computer Museum Society and Sydney's Powerhouse Museum (now the Museum of Applied Arts & Sciences, MAAS), including a section of SILLIAC, Australia's second computer. He also played a pivotal role in the Powerhouse Museum's acquisition of a substantial portion of Charles Babbage's Difference Engine No. 1 in 1995. Acting on Bromley's advice, the museum purchased the piece at auction for $400,000; it remains one of only three surviving sections of the machine (Sydney Morning Herald, 2002). Following Bromley's death, other objects from his collection entered the private market. Today, his collection is a rare example of a calculator collection with a well-documented provenance. Each object bears a label marked "Bromley", together with the year of acquisition and its collection inventory number.

You're Collecting What! Collecting computers, by Allan G. Bromley
Sidney, Australia: Manuscript of 1981 publication

Description: Draft manuscript titled You're Collecting What! Collecting computers written by Allan G. Bromley, composed of 8 pages, accompanied with the published article COLLECTORABILIA Dr. Allan Bromley (pp. 58-60) in COMDEC magazine, October 81 issue. Selected excerpt: "Apart from the relative scarcity of memorabilia dating back more than a decade or so, there are certain practical difficulties involved in collecting computers from before about 1970 [...] A more practical proposition for those determined to start yet another memorabilia/collecting trend is to collect parts of computers - printed circuit boards, for example, or a vital integrated circuity or transistor type. Babbage would no doubt be impressed".

Together with additional ephemera documenting Bromley's collecting process:
(i) Handwritten aerogramme to Frank Percival, dated 8 January 1991. After discussing his work on the Antikythera Mechanism and commenting on the progress of the construction of the Difference Engine No. 2 at the Science Museum, Bromley reflects on his collecting activities in London: "Tramping around the markets of course. But there is very little to be had and even less at a modest price. I have bought a few small items. Mostly not really new, but improvements on existing items in my collection. As always same problems with books."
(ii) Correspondence concerning collecting 'holy grails': A 1991 letter from dealer Stuart Talbot offering the Thomas de Colmar calculator No. 899 for £2,800; together with 1994 faxes from Bromley's colleague Michael Wright reporting on Stanhope calculating machines (printed on thermal fax paper with Science Museum letterhead, one of which has almost completely faded).
(iii) Collection cards. Seven cards from January 1991 documenting Bromley's purchases in London. One records: "Two slide gager's slide rule | J. Long, 43 Eastcheap, LONDON | Light staining, otherwise good condition | £38". Also included are seven accession cards from 1977, documenting the earliest phase of Bromley's collecting (initially to examine calculator mechanisms rather than to build a collection), and a further eighty collection cards of a different format dating from 1979 to 1983 (some undated), none of which correspond to objects now in The Tricottet Collection.

Provenance: Allan G. Bromley

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Slide Rules
Various makers, 20th century

Description: Suite of 15 slide rules: Linear slide rules: Sun Hemmi no. 1979-12 (15 x 3 cm) which is the first slide rule catalogued in the Bromley collection!; Unique dualistic high speed (c. 1950) no. 1981-8 (29 x 4 cm); Faber Castell (1950-1960) in plastic case, no. 1982-92 (30 x 4 cm); Kent student in cardboard case with penned note "Geoff Miller", no. 1982-95 (33 x 4.5 cm); TBD, no. 1983-40 (12 x 2.5 cm); Relay in leather pouch (1962), no. 1983-49 (17.5 x 2.5 cm); TBD in leather pouch, no. 1984-53 (15 x 2.8 cm); Regal A50LL in plastic pouch, no. 1986-4 (15.5 x 3 cm); Keuffel & Esser Co. in orange pouch, no. 1986-31 (32 x 4 cm); Nestler No-28 (1908-1911) in leather case, no. 1990-102 (27.5 x 3.5 cm); Albert Nestler in leather pouch (c. 1908-1911), no. 1997 4 (11 x 2 cm); Canovai Ottico-Roma (TBC) in leather pouch, no. 1997 5 (15 x 3 cm); Pilot 200-A in plastic pouch, no 1997 7 (20.5 x 3 cm). Circular slide rule: Fowler & Co., Manchester, with leather pouch, no. 1982-46 (7 cm diameter). Cylindrical slide rules: Otis King (15 cm long when closed, 3 cm diam.) in original box with instructions, no. 1983-94; in leather pouch (Verdigris patina), no. 1983.17.

Abacuses
Various makers, 20th century

Description: Suite of 3 abacuses: Souvenir abacus mounted on green marble base, in box, no. 1981-46 (8.5 x 5.5 cm); made of wood (some glue on back suggesting part of a wall display), no. 1982-71 (13.5 x 5 cm); made of wood, no. 1986-45 (33 x 11 cm).

Mechanical Calculators
Various makers, 20th century

Description: Suite of 3 mechanical calculators: Multi-axis adding machine 'Lightning Calculator' by Calculator Corp, Grand Rapids, Michigan, no. 1981-7 (30 x 6 cm); Faber Castell add/subtract Addiator with original stylus and dark green real leather pouch, incl. slide-rule on the back side, no. 1983-76 (15.5 x 4 cm); Pen with multiplication table, no. 1982-55 (14.5 cm).

Provenance: Allan G. Bromley, all items with Bromley sticker

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SOFTCOVER EDITION - Handbook of the exhibition of Napier relics...
Edinburgh: Royal Society of Edinburgh, 1914

Description: HORSBURGH, Ellice Martin, ed. (1914), Napier tercentenary celebration. Handbook of the exhibition of Napier relics and of books, instruments, & devices for facilitating calculation. Edinburgh: Royal Society of Edinburgh. vii, [1], 343, [13]pp. 7 plates, text illustrations. 256 x 177 mm. Original printed wrappers, with sticker "Allan G. Bromley [followed by his address]" - A celebration of Napier's pivotal role in the history of calculation, the exhibition held just five days before the start of WWI featured displays of calculating machines, as well as exhibits of other aids to calculation such as mathematical tables, the abacus and slide rules, etc. The Handbook was published in two forms: a softcover version, presented to those who registered for the exhibition; and a hardcover version issued for sale under the title Modern Instruments and Methods of Calculation. Relatively few copies of the softcover version seem to have been distributed at the exhibition, partly because the exhibition took place in Edinburgh, but mainly because war broke out just after it began [OoC 322].

Together with other collection & exhibition catalogues from the Bromley library:
(i) BAXANDALL, David (1926), Catalogue of the collections in the Science Museum, South Kensington, with descriptive and historical notes and illustrations. Mathematics. I. Calculating machines and instruments. H.M. Stationery Office. 85, [1]pp., 13 plates. Original green printed wrappers, purchased "28-3-84". Accompanied with PUGH, J. (1975), Calculating Machines and Instruments, Catalogue of the collections in the Science Museum. Science Museum, revised and updated edition of Baxandall (1926), 102 pp.. Softcover, purchased "22/8/79", w. 1990 letter from J. Shore tipped in, about the return of this catalogue (1-page signed printout, Powerhouse letterhead).
(ii) BOILERHOUSE PROJECT (1984), Robots. Victoria & Albert Museum, 60 pp.. Softcover, purchased "25-4-86". Accompanied with 1990 2-pp. letter from Michael Wright regarding the preparation of a new robot exhibit at the Science Museum.
(iii) McCONNELL, A. (1986), Geophysics & Geomagnetism, Catalogue of the Science Museum Collection. 45 pp., w. letter from M. Wright offering some catalogues.

Provenance: Allan G. Bromley, all with mark(s) of provenance, such as address sticker, stamp or penned date of purchase.

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Microscope and microscope slide collections occupy a unique and specialised niche within the broader field of scientific collections, sitting at the intersection of scientific instrumentation and the preservation of medical, natural history, and geological specimens. While the earliest microscopes emerged in the late 16th century, it was the Industrial Revolution that truly accelerated both the production and popularisation of microscopes. Although interest in microscopy spread to other countries, England remained its true home (Bracegirdle, 1998). As the epicentre of Victorian scientific and intellectual activity, London even hosted microscope shows (e.g., at the Apothecaries' Hall, 1855; Fig. 1), which must have inspired awe and fascination, hence contributing to the vogue for microscope collecting.

The microscopes were often ornate instruments crafted in polished brass with intricate detailing, blending functionality with Victorian design aesthetics. As technological innovations multiplied, collectors could begin to envisage forming coherent collections and even attempting to complete sets. One of the earliest and most significant collectors was Sir Frank Crisp, who assembled almost 4,000 items, setting a precedent for later collectors.

"Arranged" slides, defined as "any preparation where the subjects have been placed in such a manner as to be displayed to best advantage" highlight the artistry of the mounter. Each slide could require many hours of meticulous work, and only a very small number were ever produced. As a result, arranged slides are among the most iconic and highly sought-after microscope slides for collectors. They emerged in the second half of the 19th century, enabled by improvements in microscopy, whereas until around 1850 most diatom slides were strewn mounts (Davidson, 2001). Around 1867, the talented preparer J.D. Möller began arranging them in orderly rows, one specimen per species. Thus was born the Type slide, essentially a systematic collection contained on a single microscope slide. Beautiful in their own right as well as scientifically valuable, other forms of arranged slides were soon created according to purely aesthetic principles, featuring complex geometric patterns or pictures composed of hundreds of diatoms or butterfly scales. These became known as Exhibition slides or Salon slides (other names include Rosettes or artistic groups; Davidon, 2001). While J.D. Möller and Eduard Thum were preeminent in the production of exceptional Type and Exhibition slides, Henry "Harold" Dalton's celebrated butterfly-scale pictures place him alongside them among the finest mounters of the 19th century. Today, the most elaborate Type and Exhibition slides rank among the 'holy grails' of microscope-slide collecting, with collectors often seeking examples containing the greatest number of mounted specimens.

If the heyday of microscope collecting belonged to the Victorian era, these marvels of craftsmanship continued to be admired by subsequent generations, with the finest slides remaining highly sought after by collectors. This enduring fascination is reflected in the scholarly works of Brian Bracegirdle (1933-2015), the first Keeper of the Wellcome Museum, and Brian Davidson (?-?), an exceptional collector of antique microscope slides. Bracegirdle authored the standard reference work Microscopical Mounts and Mounters (Fig. 2), while Davidson published two seminal articles on arranged slides (Davidson, 2001; 2008). Together, they produced a substantial body of scholarship on the history of microscope slide mounting. Some slides from Davidson's collection, including examples illustrated in his own publications and in Bracegirdle (1998), remain preserved today. Unfortunately, his remarkable collection was dispersed through a series of auctions and was never fully documented. Rare slides and collection catalogues in the TC with confirmed or presumed Bracegirdle or Davidson provenance are accompanied by provenance notes where known.

Diatom "Typen-Platten", by Eduard Thum
Leipzig, Germany, 1875-1900s

Description: Suite of three type slides with diatoms arranged in perfect alignment, ranging from the smallest to the largest number of specimens:
(i) Type slide bearing two Thum labels titled "Diatomaceen-Typen-Platte xxx in Styrax. 100 Formen. Kat. IV, No. 3375" and "E. Thum, Leipzig. Institut für Mikroskopie. Specialität: Diatomaceen- u. Testpräp. Test- u. Typenplatten. Salonpräparate und arrangierte Schmetterlingsschuppen. Illustrierte Kataloge". We counted a total of 100 diatom specimens - We have yet to locate a copy of Catalogue IV in which this slide would be listed.
(ii) Type slide bearing two Baker labels titled "C. BAKER. Type-Slate of Freshwater diatoms from England. 244.H.HOLBORN" and "LONDON W.C.. 157 species. E. THUM preparer, Leipzig". We counted a total of 112 diatom specimens (TBC).
(iii) Type slide bearing two Thum labels titled "Rus Marin. Typen-Platte d. Diatomeen a. Frepang v. China" and "Mikrosk. Institut. 390 Formen i. Monobrom Naphtalin. E. Thum. Leipzig". Large bubble present. We counted a total of 382 diatom specimens (TBC), making this the Thum type-slide holy grail held by the TC - To date, we have not identified another Thum type slide containing more than c. 400 specimens. Stevenson (2018) notes that, by 1891, Thum had produced a slide containing 1,230 diatoms arranged in the form of a monogram, which was presented by the San Francisco College of Pharmacy to A. H. Breckenfield in recognition of his valuable course of lectures on microscopy. This demonstrates that Thum's finest arranged slides were conceived as true trophies.

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Exhibition Slides, by Eduard Thum
Leipzig, Germany, 1875-1900s

Description: A suite of three exhibition slides of diatoms and sponge spicules arranged in geometric designs:
(i) Exhibition slide composed of diatoms, bearing two Thum labels titled "Salonpräparat. Salon-Slide. Pleurosigma-Rosette. 145 Formen, Kat. VII, No. 4751" and "E. Thum, Leipzig. Institut für Mikroskopie. Specialität: Diatomaceen- u. Testpräp. Test- u. Typenplatten. Salonpräparate und arrangierte Schmetterlingsschuppen. Illustrierte Kataloge" ("5." inked below "Kataloge") - We have yet to locate a copy of Catalogue VII in which this slide would be listed.
(ii) Exhibition slide composed of diatoms, bearing two Baker labels titled "C. BAKER. Salon-Slide Pleurosigma-Rosette. 244.H.HOLBORN" and "LONDON.W.C.. 67 forms No. 4749. E. THUM, preparer, Leipzig".
(iii) Exhibition slide composed of sponge spicules, bearing two unsigned labels, likely from Clarke & Page, titled "MARINE ZOOLOGY. Echinoderma. Salon rosette of spicules &c" and "anchors of plates from Synapta (125 forms.)", together with a miniature label reading "E. THUM. Preparer, Leipzig".

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Injection/corrosion Anatomical Specimens
Vienna: Prepared by J. Hyrtl, 1860s

Description: Cased set of Hyrtl injection/corrosion specimens for the microscope, 1860s. Twenty-four slides with printed labels to the reverse. Contained in a French polished mahogany slip case with a leather label to the lid bearing gold lettering: System Lymphaticum, nervosum, fibrosum et cellulare. Each slide consists of a 45 × 30 mm ebony frame containing a central cavity in which the injected specimen is mounted in balsam beneath a glass cover (see Figures 1-3 in Hyrtl, 1873). In the appendix to his collection catalogue (Hyrtl, 1864), Hyrtl notes that his series of microscopic injection preparations included multiple duplicates of each number, intended for exchange or sale. In his 1873 catalogue, he further explains that "the preparations and the cover glass form a single unit and are therefore completely protected from all harmful external influences. The cover glasses are framed in ebony holders, with an explanatory label affixed to the back of each frame. In this mounting, the preparations are truly indestructible, withstand the roughest handling, and can even endure being stepped on without damage [...] I have preserved some of them for a period of 35 years; they are today as beautiful and intact as on the day they were made". Cases were produced in formats of 12, 24, 48, 96, or 120 preparations. In 1873, a set of 24 was priced at 20 Thalers. Hyrtl also indicates that sets could be exchanged for comparative anatomical material, including human and animal skulls (particularly exotic species), freshwater fish and reptiles from India and South America, and other natural history curiosities. These injection preparations are now considered rare survivals and are seldom encountered in private collections. It remains unclear how many sets have survived; the present example corresponds to one of only a few (4) recorded on the market in recent decades (Flints, 2020, lot 23). In the 1873 sale catalogue, Hyrtl notes that, together with remaining material from earlier catalogues, his stock comprised approximately 500 items, each with 4 to 20 duplicates, "a truly respectable stock for the new business exchanges now being initiated". It is likely that "items" refers to individual specimens rather than complete sets.

Provenance: Josef Hyrtl

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Catalog der, in der Privatsammlung..., by Josef Hyrtl
Vienna: Wilhelm Braumüller, 1865

Description: HYRTL, Josef (1865), Das Vergleichend-Anatomische Museum an der Wiener Medicinischen Facultät in Jubliläumsjahre 1865. Nebst einem Anhang: Catalog der, in der Privatsammlung des Herausgebers Befindlichen Skelete, Gehörorgane, und Mikroskopischen Injections-Präparate. Vienna: Wilhelm Braumüller, 213 pp. 213 pp. (museum catalogue) + 41 pp. (catalogue of Hyrtl's private collection). Original yellow wrappers- Published to commemorate the jubilee year of the Vienna Medical Faculty, this important catalogue documents the holdings of the Comparative Anatomical Museum, listing specimens of mammals, birds, amphibians, and fishes. The work represents the culmination of 14 years of effort and underscores Josef Hyrtl's central role in establishing the museum, which he regarded as an essential foundation for the creation of a dedicated chair of comparative anatomy. The catalogue reveals that the museum's collections were built through purchases, exchanges, and donations. The museum itself is described as comprising elegant display cabinets devoted primarily to articulated skeletons, carefully prepared and mounted in lifelike poses, alongside smaller cases housing diminutive specimens and anatomical preparations preserved in spirit. An especially significant feature is the appendix, Catalog von Fisch- und Amphibien-Skeleten, sowie von Gehör-Organen und mikroskopischen Injections-Präparaten, welche sich im Privatbesitz des Herausgebers befinden, which inventories the skeletons, auditory organs, and microscopic injection specimens in Hyrtl's own collection. Hyrtl regarded his private holdings as complementary to those of the university museum. Most of the specimens were prepared by Hyrtl himself, while others were acquired at his own expense or obtained through exchanges of his renowned injection and corrosion preparations.

Catalog Mikroskopischer Injections-Präparate, by Josef Hyrtl
Vienna: Wilhelm Braumüller, 1873

Description: HYRTL, Josef (1873), Catalog Mikroskopischer Injections-Präparate. Vienna: Wilhelm Braumüller, 40 pp., 3 figs. In original yellow wrappers, uncut - In this sale catalogue, Hyrtl showcases the exceptional quality of his anatomical injection preparations, emphasizing the superiority of his injection technique and the scientific value of the specimens offered.

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Perlen aus der Instrumenten-Sammlung von Paul de Wit
Leipzig: Paul de Wit, privately published, 1892

Description: DE WIT, Paul (1892), Perlen aus der Instrumenten-Sammlung von Paul de Wit, Leipzig. Leipzig: Verlag Paul de Wit. 14 pp., 16 chromolithographic plates by Emil Pinkau, descriptive text in German, French, and English. Oblong folio, original board wrappers preserved in a specially made binding, upper cover with central sunken panel featuring a colour illustration of four musicians, with elaborate metalwork in each corner:
(i) Presentation copy in velvet binding, inscribed: "Hommage de reconnaissance et de sincère admiration de la part de l'auteur! Leipzig, 3 Octobre 1903, Paul de Wit".
(ii) Presentation copy in grey (or discoloured) binding, title page taped, inscribed: "Souvenir de l'éditeur à M. le dr. Maurice Emmanuel de Paris, Paul de Wit, Leipsic, le 26 Octobre 1897" - Maurice Emmanuel (1862-1938) was a French composer and musicologist and one of the genuine independents in French music.
The album was likely issued in connection with the 1892 theatre and music exhibition in Vienna.

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