11C with no serial number!?


I just obtained an 11C which appears to have no serial number anywhere. Also, it differs from two other 11Cs I have in that the keyboard overlay has a matte (nonreflective) finish rather than glossy. The 11C logo on this unit has a bright silver (mirror) finish. My other 11C has a more of a matted silver 11C logo (the third one is missing the logo).

Does anyone know where I can find the serial number on this unit? It does not appear to be altered. I've inspected the area where I'd normally find the serial number carefully, but it looks clean and uniform throughout with no signs of alterations or tampering. The rest of the body appears the same (clean, uniform, no signs of tampering if serial# has been somehow erased).

This unit is very clean overall (maybe a 9.6) so it would seem it "should" be easy to find signs of tampering... but I don't see any.

Has anyone seen such an 11C (or any other Voyager series calculators with similar features)?

Thank you in advance,


My guess is that this was a replacement unit sent out in exchange for one that was returned to HP for repair. I've heard that some of the calculators HP used for these exchanges didn't have serial numbers. It would also explain the other differences you mentioned, since HP often manufactured replacements even after the "for sale" units had gone out of production. Slight changes might be made after the regular production stopped, and so these differences would only be seen in the replacements, which would be less common than the production units.


I am looking for a users manual for my HP 12C??


I am looking too a users manual for my HP12C.
This manual is always sold by HP, but the price in France is prohibitive : # 35 $......
So, if you find solution, I'm interested...


Could it also be possible that the HP serial number stamping machine spat out a few calculators with no serial number and quality control did not pick this up until some units had gone out?

If so I wonder how many 'escaped' with no serial number?


I have a HP16C with no serial number. I got it from its
original owner and he didn't mention anything about
it being a repair unit. Cosmetically it looks just like
the other HP16C I've got, with the exception of no serial
number stamped anywhere on the unit.

I'd also be interested in hearing if others have seen this on other Voyager models.

Alex Knight
The Electronic Calculator Museum Web Page



for the mirror-like logo: These were used on the older machines. Later machines have the matted logo.

For the missing serial numbers:
I have an HP-41C with no serial number, and an HP-41 card reader with no serial number, too.
Their cases were replacement parts which certain companies could buy from HP for their special hardware extensions (W&W RAM boxes, etc.)
Empty printer plug cases w/o date code were available, too.



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