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APF MARK 55

APF MARK 55
Image: wass.net used with permission

The APF MARK 55 is a scientific calculator with 12 digits precision and RPN (reverse polish notation) logic. It has 45 functions, 30 keys, and an LED (light-emitting diode) display, typical of calculators of this era. The power source is 3xAA sealed. Note: Similar to HP calculators.

Facts at a glance:

FeatureValue
TypeScientific
Functions45
Keys30
Precision12
LogicRPN
Display typeLED
Length159mm
Width76mm
Power Source3xAA sealed
Year introduced1977

Replacements:

If you have an APF MARK 55 that is no longer working, you can first try replacing the 3xAA sealed batteries. If that doesn't solve the problem, then you can consider replacing the calculator with a modern equivalent. We suggest the following current model as a replacement:

See other calculators by APF