HP41C halfnut serial numbers

[David Smith]

I recently got an HP41C HALFNUT. It had a serial number of 1932A00XXX. This number was 13 off from my old full-bugs, gold ball, tall key unit. This seems to support the theory that the halfnut 41C's were very late date service replacement units. For a service replacement they swapped the old case back onto the new halfnut front end to keep the old serial number. If you had a damaged case back, you got back a new case back with a hand-engraved serial number.

[Randy Sloyer]

That would make a lot of sense. Why not just replace the front with current production and give the customer his old serial number back. I guess the older case bottoms without the extended cylinders on the bottom screws didn't matter on a half-nut?

This gives rise to the question: Was the C just a CV with a trace cut for the reduced memory? I doubt they masked a separate chip for just the C's. Maybe they just dropped a wire bond or two at packaging. I read the memory was in the display module, I believe Luiz did or at least tried to confirm this a few months ago. Maybe the module part numbers will tell the story?

[David Smith]

HP was rather agressive about keeping a unit's serial number when the case was replaced during service. I know a lot of calculators back then were kept under inventory control systems. Changing a serial number could cause a lot of user headaches.

I have not opened up the halfnut 41C yet to see what differences it has with the CV. It is definitely a 41C halfnut (with quad memory module plugged in).