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).

Made by Corvus Corporation, of Dallas, Texas, a subsidiary of Mostek, the Semiconductor manufacturer.

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

 

This model was reviewed in Popular Science[2]:

"Electronic Checkbook remembers your balance
When l tapped an imaginary checking-account balance into Mostek Corp.'s new CheckMaster, I was amazed to learn the electronic checkbook would remember the dollars-and-cents figures for up to one year. Six penlight cells power the unit's low-current memory. As you write checks or make deposits, you perform arithmetic with CHECK, DEPOSIT, and BALANCE keys. And CheckMaster shows the overdraft amount, if any. (Jot down your balance and you can also use CheckMaster as an add-subtract calculator).
bur.) The $40 eight- ounce unit is 7/8 by 3 5/8 x 6 3/4 inches. Distributor is JS&A National Sales Group, 4200 Dundee Rd., Northbrook, Ill. 60062."

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

References:

  1. Popular Science, June 1975, p133.
  2. Popular Science, August 1975, p11.

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© Text & photographs copyright Nigel Tout   2000-2017  except where noted otherwise.