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Calculators: Handheld: Boots 224 Memory (Type 2)

Size (approx): 77mm (max) x 136mm x 19.7mm (max)  (w,h,d)
Weight 108g excluding batteries

Power:

3V DC, 2 x AA size battery, 0.2W.  Also accepts adapter.  Socket on top side on the left.  Quoted manganese battery life time is 8 hours.
Case: Slim design which fits in the hand well with on/off switch in thumb position on the top left side.  Cream plastic base and brown smooth plastic top inset with brushed aluminium panels above display and around keys.  Logo and model printed on the top has survived well.  Extra switch for decimal rounding control.  Very slight tilted and flush display filter makes this a nice blue shade display.  Nice design by Casio as this is a "made for a brand" calculator.
Display: 8 digit blue VFD (no ninth digit)
Features: 4 function calculator with percentages, delta percent, square root and three function memory
Age: 1978 (guarantee dated 12 May 1978)
Manufacturer: Boots.  Made in Japan (actually a Casio).  Serial number 3D707A printed on the inside of the battery cover.
Comments:

 

You just know this is a Casio!  Only let down by the lack of a ninth digit - hence you can only have seven digit negative numbers, and you can have negative roots.  I think the blue button colour , however, is an improvement on the original Casio H-1.  Original cover is soft black plastic with open top and "Made in Japan" embossed on the reverse.  There is a Type 1 which just appears to be a case change and small board revision.

Components: 1 x cpu: NEC D1877C 8306K9 Japan - 28 pin DIL
1 x display: Single flat glass tube digitron, eight digit VFD, NEC LD8225 Japan
1 x transistor
7 x diodes
7 x capacitors
4 x resistors
1 x transformer;TC-11 3 4 TDK
Boards: Main board (Ref G1G-1B) is connected by 16 copper wires to the (and sits on top of the) keyboard board.  The latter is secured to the front by 5 screws.
Construction: Remove the single screw from the back and gently prize from the bottom.

Logic comments: The (C) button is used to clear last entry of a number and (AC) to clear the whole calculator.
Overflow on number input is suppressed, typing in a nine digit number ignores the ninth digit.
There is selectable automatic constant on all four function by double hitting the operator; i.e. (3)(X)(X)(=) gives "9".
An overflow error is flagged with an "E" in the first (right most) digit, negative or positive.  Number is not recoverable.
Divide by zero shows an  "E" which is also not recoverable.
Square roots of negative numbers are allowed
AC cancels the memory as well, there is no indication of memory store - you have to remember it.
Negative numbers are flagged by a "-" sign in the immediate left digit, limiting you to seven digit negative numbers.  If you type in (-)(1)(2)...(8)(=), this will result in an error.