Heathkit Navigation RPN Calculator OC-1401 Computer with Box

Description

Heathkit Navigation Calculator OC-1401 Computer with Box. Condition is "Used".
The calculator/computer works when powered from a lab power supply as shown in the images. The external power supply, when plugged in, i would have expected to light up the LED included however it does not so i didn't connect it to the calculator, i was afraid it might damage the calculator. I didn't take the power supply apart however i expect it to have a constant current circuit to recharge the batteries and a constant voltage circuit to power the machine while charging. The HP classic family of calculators uses a similar mechanism, up to and including the contact between the two side pins of the calculator connector when a charger is not connected.
The calculator had 4NiCd rechargeable batteries inside which i removed (batteries will not be shipped, they were recycled). The old batteries are shown in one of the images for exemplification. I tested the computer with a 6VDC lab power supply and it seems to work well, all LED segments work and i was able to perform simple arithmetic. The calculator is one of the very few non-HP RPN machines.
Please note that if the case is open you will have to make contact between the side pins of the connector somehow, to power the calculator from the battery terminals (last image, I used a cable with alligator clips at both ends). If the case is closed, the contact is made by a metallic bracket, same as for the HP-35.
The plastic box is in poor shape, the lid is detached and the closing flap is also almost broken.
A quick reference guide is included.
I used to have the manual but i seem to have lost it because i could not find it. The manual doesn't fit in the box so it was stored separately in a safe place. Well, it is safe, nobody can find it. So the manual is NOT included, but if i find it, i will ship it together with the calculator.
This is a very rare piece of electronics and because of the unprotected batteries inside many survivors were damaged by leakage from batteries. This one still works!