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Calculators: Handheld: Casio Memory B-1 (aka H-816) 

Size (approx):

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


3V DC, 2 x AA size battery, 0.2W.  Also accepts adaptor (AD-2S, centre negative) through a socket on the top side on the far left. 
Case: Two piece smooth plastic case in white and dark brown.  It is quite slim and fits in the hand well.  The front has two brushed aluminium panels, the top one bearing black and blue printed company and model info and the keyboard surround a few black labels.  They keys are bouncy with the usual Casio miniature escutcheons which give that quality feel. The on/off switch is on the left hand side in line with the Casio text and is recessed to protect it.  The neutral display filter is very slightly titled and gives a clear bight image.
Display: 8 digit blue VFD with no ninth digit.
Features: Four function with square root, percentages, delta percent, switched floating/ 2 decimal point and three function memory.
Age: est 1978
Manufacturer: Casio Computer Company Ltd, made in Japan, serial No. (inside battery compartment) 0008545. 


Nice quality Casio model that has survived well.  Logic is let down by seven digit negative numbers, negative roots and lack of overflow recovery.  Original case is soft black plastic with open top and concave top edges.  It is embossed with "Casio" on the from and "Made in Japan" on the back. A version of this calculator was the 224 Memory for Boots.

Components: 1 x cpu: NEC D1877C E87346, 28 pin DIL, 0.6" width
1 x 8 digit VFD display: flat faced glass unit; NEC FIP LD8225/FIP8A5 No. 8J, Japan
1 x transistor
8 x diodes
12 x capacitors
3 x resistors
1 x transformer
Boards: The main cpu board (ref F8X-1A) sits loosely on top of the keyboard assembly and is joined by 16 strong copper wires.  The latter is fixed to the front by five screws.
Construction: Remove the single screw from the back and gently prize off the back which is attached with three lugs on the sides and two on the top.  Warning, it is quite difficult so if in doubt don't do it as you may damage your calculator.  The main board has very good labelling (i.e the display has a LD8225 / E6603 AC/DC label) and space for extra/alternative components.

Logic comments: (C) cancels an incorrect numerical entry and (AC) for all clear clears the calculator
There is manual constant (hit function twice) on all four functions; i.e. (6)(+)(+)(=)(=)... will continue to add six.
Input overflow is suppressed, inputting a ninth digit is ignored
Negative sign is shown in the immediate left hand digit but having no ninth digit to travel to limits you to seven digit negative numbers. 
Divide by zero shows "E" which is not recoverable
Overflow is shown by the result with the final (right hand) digit set to "E" and is not recoverable
Memory store is not indicated - you have to remember it
The (AC) function clear the memory as well, which is annoying if you have added a number to memory which results in an error as you loose the lot.
Negative square roots are allowed and result in a negative number
There is a switch on the front that toggles between floating decimal point, "round down" and "round" for fixed two decimal places.
It suffers the divide to negative zero (once) bug: key in (1)(M-)(1)(0)(/)(/)(MR)(=)(=)(=)... etc to give "-0", one more (=) will give zero so this is presumably an artefact of the extra digit of precision

Footnotes: Additional serial numbers I have had: 05476496 and 0825853
Serial number from SL in the UK: 0173167