Hand-held Calculators

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Check, Billfold, & Wallet Calculators

The calculators on this page are specifically intended to be carried in the pocket and some can maintain a balance of money.
Their names reflect this by incorporating "Check" (Cheque in the U.K.) or "Billfold" (Wallet in the U.K.), and for their year of manufacture they are especially slim so that they do not leave a bulge in the pocket.

The calculators featured on this page are:

Check Tronic

Check Tronic
Check Tronic closed

Check Tronic

Distinctive features: Cheque (check) account calculator. Balance still stored when switched off.

Technical details:
Display is 8 digits, red LED.

4-function.

A standard 4-function calculator incorporated in a wallet for balancing a bank cheque (check) account.
Unusually for this early date, the balance is stored even when the calculator is switched off, and can be recalled when switched on again. This is achieved by maintaining power to at least the memory.

9v (PP3 battery).

About 1975.

Manufacturing company not known (has logo which may be "AD").
If you have more information about this model please get in touch with us.

Corvus CheckMaster

Corvus CheckMaster

Corvus CheckMaster

Distinctive features: Very basic cheque (check) account calculator. Only has "+" and "-" functions. Balance still stored when switched off.

Technical details:
Display is 6 digits, red LED.

2-function.

This is a very basic calculator in a folding case for balancing a bank cheque (check) account. The display has a fixed decimal point for currency calculations, there is no decimal point key, and the only functions that provided are "Deposit" (add) and "Check" (subtract).
Like the Check Tronic above, the balance is stored even when the calculator is switched off, and can be recalled when next switched on. Again this is achieved by maintaining power to at least the memory.

9v (6x AAA batteries).

In June 1975 JS&A National Sales Group was selling this model at the "introductory price" of US$39.95[1].

Made by Corvus Corporation, of Dallas, Texas.

Corvus CheckMaster closed

The Corvus CheckMaster closed.

Corvus CheckMaster batteries

With the battery cover removed, showing the 6x AAA batteries.

The Check Tronic and Corvus CheckMaster calculators above have the unusual feature, for this early date, of storing a number when the calculator is switched off. This is achieved by maintaining power to, at least, the memory and requires the very low power consumption possible using C-MOS (Complementary Metal Oxide Semiconductor) integrated circuits. However, if the batteries are removed the number is lost.

The Corvus CheckMaster is probably the least capable electronic calculator ever marketed, since it is only capable of addition and subtraction, though this is all that is required for its design purpose.

Novus Billfold 91

Corvus CheckMaster

Novus Billfold 91

Distinctive features: Cheque (check) account calculator. Takes unusual Flat-Pak battery.

Technical details:
Display is 8 digits, red LED.

4-functions, %, memory, square-root.

This is a really just a slim calculator incorporated in a billfold (wallet), and, unlike the Check Tronic and Corvus CheckMaster calculators above, it does not retain memory when the power is switched off.

9v special Duracell "Flat Pak" battery.

This example appears to be a promotional item for the preview of the 1977 range of Buick, Oldsmobile, Pontiac, and GMC motor vehicles, which was held on June 16, 1976.

Made by in U.S.A. by National Semiconductor.

Corvus CheckMaster

The calculator is unusual in that it is held in the billfold by extensions of its circuit board which pass through slots in the synthetic leather.

The calculator must be removed from the billfold to replace the battery.

Back
Battery

The battery used in the calculator is a very unusual 9 volt Duracell "Flat-Pak".

Chip

The semiconductor chip used in this calculator is directly mounted on the circuit board and then encapsulated in a blob of resin for protection. This reduced the cost but was very unusual for the time, though is now very common.
National Semicinductor also used this technique in its Novus 650 "Mathbox" calculator.

Radofin 1720

Radofin 1720
Radofin1720_2

Radofin 1720

Distinctive features: Cheque (check) account calculator. Takes unusual Flat-Pak battery.

Technical details:
Display is 8 digits, red LED.

4-functions, %, memory.

This calculator is similar to the Novus Billfold 91, above. Again it is a really just a slim calculator incorporated in a billfold (wallet), and, unlike the Check Tronic and Corvus CheckMaster calculators above, it does not retain memory when the power is switched off.

85 x 170 x 12 mm / 3.3 x 6.7 x 0.5" (calculator only).

6-off AAA batteries.

Radofin Electronics Ltd.
Hong Kong

Reference

  1. Popular Science, June 1975, p133.
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Hand-held Calculators

TI Cal-Tech
Canon Pocketronic
Sanyo ICC-0081 & ICC-82D
Sharp QT-8B
Busicom LE-120A & LE-120S
Sharp EL-8 & Facit 1111
Minolta Minolcom
Brother PRO-CAL 408
Walther ETR3
Bowmar 901B
Ragen Microelectronic
Compucorp 324G
Sharp EL-811 & derivatives
Royal Digital III & IV
Busicom LE-100A handy
Busicom LE-80A handy
Hewlett Packard HP-35
Canon LE-10
Rapidman 800
Texas Instruments 2500
Lloyd's Accumatic 100
Sinclair Executive
Casio Mini
Sanyo ICC-809
Sharp EL-801
Texas Instruments SR-10
Sperry Remington 661D & 661
Olympia CD 81
apf Mark V
Ramsgate M-11
Olivetti Divisumma 18
Iain Jones International Mini A
Hewlett-Packard HP80
Litronix Checkmate
Heathkit IC-2009
MITS 150
Summit Ko9V, K16 & SE88M
Unicom 102
Victor 85 "Tallymate"
Elka 101
RFT minirex 75
Sharp EL-120
Sharp EL-805
Bowmar MX-55
Atlas-Rand, Berkey, & Keystone
Hewlett-Packard HP-65
Casio fx-10
Calcu-pen
Casio AL-8 & family models
Commodore 776M & 796M
Novus 650 "Mathbox"
Rockwell 8R
General Instrument EZ3000
Check, billfold, wallet calculators
Monte Carlo
Texas Instruments Spirit of '76
Pulsar Calculator Watch
Compuchron Calculator Watch
Adler Lady & Sir
Elektronika B3-18A & C3-15
Speech+
Commodore S61
"Standard Type 1"
Sharp EL-8026
Texas Instruments TI-30
Canon Multi 8
Casio ST1
Wrist Calculators
Kosmos I & Kosmos Astro
Hanimex Calculator-Recorder
Navigation Calculators
TI58 Special Function Calculators
Sandvik 842S Coromant
"Standard Type 2"
Panasonic Electronic Ruler
Teal Photon
Casio Mini Card LC-78
Feet & inches calculators
SCAT Specialist Calculators
Sharp EL-826
Sharp EL-825
Sanyo CX-1
Elektronika MK-33 etc
Sharp PC1211/Tandy TRS80 PC1
Curta
Slide Rule
Otis King L

Vintage Calculators

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