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Calculators: Handheld: Unimark 805T

Size (approx):

90mm (max) x 140mm x 25mm  (w,h,d)
Weight 150g excluding batteries.

Power: 6.0V DC, 4 x AA size batteries, 0.5W.  Also accepts adaptor/charger (undefined) through a top side socket on the right.  The battery compartment has a ribbon pull to help remove the batteries.
Case: Solid square shaped calculator made from a two-piece light buff gloss plastic. The green display filter is flat and flush with the case and gives a clear bright display.  A brushed aluminium panel sits in its own recess and has a printed logo, model and on/off indicator.  They keys are soft, long travel and very spring but work well.  A nice matt blue plastic panel surrounds the keyboard. 
Display: 8+1 digit green VFD display the ninth used for minus and error signs.
Features: Basic four function with percentages and power save
Age: 1975
Manufacturer: Manufacturer: Interpur, PO Box 2353 Orlando, Florida USA.  Made in Japan.  Serial No. 916560.  Also seen Serial No. 884013
Comments: A well-made calculator that is nice to hold though rather on the large side.  Reasonable logic and an inspired choice of keyboard surround.  Original case is soft black plastic with flip over flap and tuck in strap on the front. 

Components: 1 x IC: Texas TMS0851NC 7538 (week 38 of 1975)
1 x VFD: 9 digit single round faced glass
2 x transistors
3 x diodes
5 x capacitors
20 x resistors
1 x transformer: 517A
Boards: The main keyboard assembly (J CA1905-01) sits loose on top of the battery compartment and is connected through 15 strong wires.  The main board is held to the base with a plastic pillar and guide lugs.
Construction: There is a coin lever slot at the top (which originally had a guarantee sticker over it), but this is not much help as the case sides are so stiff.  Trying to open it is not recommended as damage may result. The lower section mush be pushed in to pop the numerous lugs.  Even with a top, bottom and one side popped it is still difficult top open.  the top section will lift off.

Logic comments: The Clear key (C) is used once to clear an input number and a second time to completely reset the calculator
Overflow on the input of a number is suppressed typing in a ninth digit is ignored
The automatic constant is on all four functions
The negative sign is shown immediately to the left of the number, travelling into the far left (ninth) digit, thereby allowing full eight digit negative numbers.
An overflow is shown with the result and a C (E if negative) in the far left (ninth) digit and is recoverable using (C).
A divide by zero or overflow error is shown by a "C" in the far left (ninth) digit and is recoverable. Using (C).
There is a power save function, after around 25 seconds the display will switch off except for a "-" in the ninth (far left) digit and pressing the (<>) key restores it to normal.
It suffers the pseudo fixed decimal bug: key in (1)+(0)(.)(0)(0)(0)(=) and the answer will be "1.000" which will remain a fixed three digit number until multiply or divide is used, or more digits are needed.