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Calculators: Handheld: Sperry Remington 667

Size (approx): 76mm x 130mm x 25.8mm  (w,h,d)
Weight 136g excluding batteries

Power:

3V DC, 2 x AA size batteries.  It accepts an adapter (AD-2S 0.18W),  through a socket on the top side to the far left.  Battery life is quoted at 10 hours (manganese) and 22 hours (alkaline)
Case: Two piece case made from matt white plastic with rounded corners and edges.  The display filter is a neutral window of a larger matt black plastic section that wraps around the vertical edges.  Within this, sitting in its own recess is a black printed metallic sticker with the brand and model number.  The recess on/off switch has a green dot to indicate the on position.  The large keys are long travel, with a hollow metallic click, very similar to Casio ones of this era.
Display: 6 digit blue VFD with no seventh digit.  Lower segments used for zero.
Features: Four standard functions with display shift
Age: 1974
Manufacturer: Sperry Remington is a trademark of Sperry Rand Corporation.  Serial number 4011170 or 5113318 in battery compartment. 
Comments:

 

Smaller solid feeling calculator that is very similar to some Casio models.  Early 6-digit with shift display is novel.  Even more novel is the use of the lower segments only for the zero symbol.  For zero, it uses the lower half of what we would normally see an "8" displayed.  Logic is poor with no recovery, you cannot manipulate 12 digit numbers, negative zero bug, divide to zero bug and divide by zero counter bug - phew!  This appears to be a small, slight later version of the Sperry 665.  The original case is soft black plastic with top popper closing.

Components: 1 x cpu: NEC µPD178C K47706, 28 pin DIL 0.6" width black plastic
1 x single glass tube 6-digit VFD display
14 x capacitors
3 x resistor arrays
2 x resistors
1 x transformer converter unit TDK CD14202 04XC
Boards: The main cpu board (6X-1A) sits on top of the keyboard assembly (6X-E4A) supported by plastic posts.  They are connected via 9 strong wires.
Construction: To open, undo the single screw hidden in the battery compartment.  Then you have to pop the internal lugs which is quite difficult.  Start by pushing in the rear section side by one of the lower corners and work your way around 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, keying in a seventh digit is ignored
An overflow shows the result and is not recoverable
Divide by zero results in a  "000000." which is also not recoverable, however, if you press the (>) key you will see a the clock counting
There is automatic constant on all functions functions
The arrow key lets you see the other six least significant digits but it then is unrecoverable
Negative numbers are flagged by a "-" sign in the sixth (on the far left) digit, limiting you to five digit negative numbers. Also, the least significant bit displayed will show the negative sign in the first digit.
It suffers the negative zero bug: key in (1)(-)(2)(=) to give "-1" now key in (+)(1)(=) to give "-0".
It also suffers the divide to negative zero bug: key in (AC)(-)(1)(=) to give "-1" then key in (/)(1)(0)(=)(=) etc... to eventually give "-0"

Sperry 667 manual The manual on the left measures 100mm by 64mm and is 20 black and white pages.  This example is in French and Germany only.

It is full of instructions, extensive examples and specifications.

Printed in Japan.

Note the unusual way that zero is represented - by only using the lower half of the digit.  It is believed that this configuration would allow a single segment to go out and yet not confuse two different digits.