Question about HP-41C Serial #


I recently bought a nice 41C which serial number begins with 2043A.
The machine has a halfnut display. As far as I can see on hpmuseum pages, early machines had a fullnut display. Though I assume this is an early model, I know little about this issue.
Can someone let me know if halfnuts were already marketed on the 2nd year of Hp41 production in the states ?


No, they (half-nuts) did not appear until 1985 or so. What you have is a unit that was returned for repair late in the game, after they stopped fullnut support so HP service just stuck the old back on a new front half of a replacement calculator.

It would be interesting to know if it truly has only 46 free registers or if it is really a CV with a C label on it.


46 reg free.
Also, gold-plated ball-bearings are present, which I assume is consistent with the serial #.
So I think you got it right,
Thanks very much for your help Randy !


Hmm. So either they made some halfnut 41Cs specifically for replacements like this, or else they hacked a 41CV to make it act like a 41C. And what HP hacketh, perhaps ..


I believe Wlodek's guide to HP's says that HP made a very small number of halfnut 41c calculators for replacements.

They are quite hard to find and worth $$ to collectors who truly want one of everything.


Sorry, forgot to add that since a CV defaults to 46 free, you've got to do an [xeq] [alpha] [size] [alpha] [000] to know for sure. Chances are it is a HP hacked C version of a halfnut CV. Several have been reported here and yes, the gold ball contacts are consistent with an early C case back. Consider yourself lucky, it still remains the only 41 variant I do not own along with many other 41 collectors, marble blue and clear cases non-withstanding.


Thank you all for these informations.

Actually, even when resizing the memory allocation I get 00 reg 63, so I believe it is a 41C. Is there a way to know if the machine was rebuilt by HP ?

Actually I know little about it and I even don't know if the half-nut/full-nut mask can be (easily or not) separated from the rest of the machine...

However, I understand from your inputs that this may be an HP "re-creation" and that I should keep this one as a collection piece.

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