Collecting

Fluorescent-display calculators are the easiest of the early electronic calculators to collect. Millions were made, many still work, and most cost less than a meal. At the top of the field are the first machines, the single-tube Sharps and their clones of 1969–72, which are scarce and sought after. Between the two lies a huge range of pocket and desk machines from dozens of brands, many of them good-looking, nearly all of them cheap, and very few of them documented.

Figure 1 — Ten members of the Casio Mini family of 1972–75, with their round multi-digit tubes: the commonest VFD calculators, and the easiest place to start. — Photo: 軍事用懐中電灯, Wikimedia Commons, CC BY 4.0.

9.1 What is common and what is rare

Common (about $10–50): the Casio Mini, Personal-mini and Pocket-mini; the Sharp ELSI MATE pocket machines of the mid-1970s; Commodore, Unisonic, Lloyd’s, Craig, Rockwell and the many other American-badged pocket machines; and almost every fluorescent desk machine of the later 1970s and 1980s, which often sell for a few euros.
Less common: the early scientifics (Casio fx-10, fx-20, fx-101, fx-201P; Sharp PC-1802 and EL-5001), the Casio CQ-1 clock-calculator, and the first-generation Casio and Toshiba desk machines with single tubes.
Scarce and sought after: the Sharp QT-8D and QT-8B, the EL-8 and EL-8M and their Facit 1111, 1115 and Addo-X clones, the Burroughs-badged Sharps, the Busicom Junior and NCR 18-16, the Friden EC-1117A, and the Sharp CS-16A, which as the first VFD calculator of all is rarely seen outside Japan. The Calcuseum database rates the QT-8D and EL-8 at 8.5 out of 10, against 7.5 for the Casio Mini CM-602.

Figure 2 — A Sharp QT-8D Micro Compet beside a Compet 16: the four-chip machine of 1969 against the desk machine it replaced. — Photo: Rick Bensene, Old Calculator Web Museum, oldcalculatormuseum.com.

9.2 What they cost

Asking prices from eBay listings, plus a few sold results from Catawiki; none of these is a statistical guide.

Table 1 — What they cost

Machine	Price	Kind	Source
Sharp EL-8A, working	about $285	asking	eBay.de
Sharp EL-8, working, 1971	about $225	asking	eBay.de
Sharp EL-8, untested, no adapter	about $119	asking	eBay.de
Casio Mini CM-602 with case	about $20	asking	eBay US
Casio Mini with case and batteries	about $49	asking	Etsy
Casio √121-S desk, twelve-digit VFD, 1973	€24	sold, no reserve	Catawiki
Sperry Remington SSR-8, about 1974	€3	sold	Catawiki
Cimatron Escort desk, VFD	about $40	sold	eBay.de

For comparison, the machines new: Sharp QT-8D, $395 in 1970 (¥99,800); QT-8B, $495; Sharp EL-8, $345 in 1971 (¥84,800); Casio Mini, ¥12,800 in 1972, and $59.95 in the United States that November.

9.3 Search terms

The display has many names, and the sellers use all of them:

“VFD calculator”, “vacuum fluorescent”, “fluorescent display”, “green display”.
Maker names for the tube: “Itron” and “Iseden” (Ise Electronics), “Digitron” (Casio’s word in its manuals), “FIP” (NEC).
Sharp’s family names: “ELSI”, “ELSI MATE”, “Micro Compet”, “Compet”. Commodore’s “Green Line”.
Tube type numbers, which some sellers quote: DG10L, DG10B, DG12B, DG12C, 9-ST-, 9-CT-, 13-MT-, LD80.
In other languages: “Taschenrechner VFD” or “Röhrenanzeige” in German, “calculatrice VFD” or “afficheur fluorescent” in French, “蛍光管電卓” or “蛍光表示管電卓” in Japanese.
Model numbers, always.

9.4 Where to look

eBay, especially eBay.de and the other European sites for office machines, and eBay US for the American-badged pocket machines.
Catawiki, which holds weekly calculator lots and shows its sold results.
Kleinanzeigen in Germany, Leboncoin in France and Marktplaats in the Netherlands for desk machines from offices.
Yahoo! Auctions Japan and Mercari Japan, through a proxy service such as Buyee or ZenMarket: the deepest pool of Casio, Sharp, Canon and Toshiba fluorescent machines, including the early desk models. The Japanese searches above help.
Barnebys, which gathers auction-house lots; Etsy for pocket machines; and the classifieds of the Hewlett-Packard Museum forum.

9.5 Before buying

The battery compartment. Look for corrosion, a leaked pack and rusted springs. This is the commonest fault, and the most often hidden in photographs.
The display lit. Even brightness from end to end and on every segment; no white or flaky patch where the getter should be a silvery mirror.
The keys. Every key registering once, without bounce or sticking.
The adapter or charger. A special connector, as on the Sharp EL-8, the Royal Digital V and several Sanyos, is hard to replace. An original adapter adds value.
The rechargeable pack. If there is one, treat it as dead and price in the repair.
A test. If the machine can be tried, run its manual’s examples, including the overflow; for a QT-8D or EL-8, the decimal point call-back as well.
The extras. The original box, manual and case all add value.

9.6 Weights, for shipping

Pocket machines are light. Early desk machines are heavier: the QT-8D weighs 1.4 kg and the CS-16A 4 kg. All the tubes are glass, and single tubes on flying leads are fragile: pack a desk machine so that nothing can press on the display window.

Figure 3 — A Unisonic 890C pocket calculator of about 1975, with a fluorescent display and a sealed battery pack: one of the hundreds of inexpensive VFD machines sold under American brand names. — Photo: Joe Haupt, Wikimedia Commons, CC BY-SA 2.0.

Figure 4 — A Casio Memory-8A of about 1974, with a green fluorescent display: a typical mid-1970s Japanese pocket machine, and easy to find. — Photo: Joe Haupt, Wikimedia Commons, CC BY-SA 2.0.

Figure 5 — An APF Mark 30, made in Japan in the 1970s, with a woodgrain top and a fluorescent display. — Photo: Joe Haupt, Wikimedia Commons, CC BY-SA 2.0.

Figure 6 — A Rockwell 24K of about 1975, made in Taiwan, with its fluorescent display, beside its original box. — Photo: Joe Haupt, Wikimedia Commons, CC BY-SA 2.0.

Figure 7 — A Qualitron 1438 conversion calculator of 1975, with an Itron FG95A flat nine-digit tube. — Photo: John Wolff, John Wolff's Web Museum, johnwolff.au.

Figure 8 — An Adler Scientific 108T of 1975, with an Itron FG125A2 flat tube showing eight digits and a two-digit exponent. — Photo: John Wolff, John Wolff's Web Museum, johnwolff.au.

9.7 Museums and online collections

Whipple Museum of the History of Science, Cambridge: the Francis Hookham collection of calculators, catalogued online with photographs, including the Sharp EL-8, Canon LD-81 and Casio fx-201P.
Smithsonian National Museum of American History: a large collection of hand-held calculators, many of them VFD.
Ridai Museum of Modern Science, Tokyo: early Japanese calculators.
Old Calculator Web Museum (Rick Bensene): detailed exhibits of the Sharp QT-8D, EL-8, Burroughs C3260, Busicom 120-DM, Friden EC-1117A, Casio Mini and Crown CL-80K.
John Wolff’s Web Museum: maker-by-maker pages with tube and chip identifications and repair notes.
Brent Hilpert’s Early Electronic Calculators: schematics, measurements and fault logs.
Calcuseum: a large database with ratings.
Vintage Calculators Web Museum (Nigel Tout), with its pages on display technologies.

9.8 The documents in the Library

Everything in the Reference Library for this series:

The tube: Tanji’s patents US 3,508,101 and US 3,723,789; Ise’s US 3,786,295 and US 4,081,716; Ise’s papers of 1976, 1979 and 1983; the Electronics report of 1967 and two Japanese newspaper reports of July 1967; the Hitotsubashi case study of Ise Electronics.
Tube data: the Ise Itron DG-12C and DG-19 datasheets of 1968, with a later scan of the DG12B sheet; the Soviet IV-4 and ILC1-8/8LV sheets.
Driving the display: Noritake APN201, Allegro’s VF Display Fundamentals, National Semiconductor AN-440, and the Microchip HV5812 datasheet.
Chips: the TI TMS 1000 Series Data Manual of 1976, the TMS0117 datasheet, the Mostek Integrated Circuit Guide of 1974, a Mostek calculator-chip advertisement, Rockwell’s MOS LSI building blocks for calculators of 1971, the GI Data Catalog of 1976, National’s MOS integrated circuits of 1974, and Trinity College Dublin’s catalogue entry for a Busicom machine, with Joerg Woerner’s notes on the Mostek chips.
Schematics: twenty of Brent Hilpert’s redrawn schematics of VFD machines, listed in the inside volume, and the Sanyo ICC-0081 logic circuit diagram.
Owner’s manuals: the sixteen manuals listed in the operating volume.

9.9 Gaps

No factory service manual for a VFD calculator has been found online; Calcuseum catalogues several Toshiba, Panasonic, Casio, Rockwell, Sharp and Olympia service documents in its own collection. No datasheets for Futaba, NEC or Ise multi-digit calculator tubes have been found. The prices above are almost all asking prices; sold results on WorthPoint and eBay could not be reached.