How many versions of the HP-35 are there?


According to this museum and many other sources there are 4 production versions of the HP-35, to wit:

1) Version 1, aka Red Dot
2) Version 2, no red dot
3) Version 3, front label with 35
4) Version 4, wider top keys with legends and raised OFF/ON legends

However, there appear to be two variations of the Version 2:

Version 2a - very similar to Version 1 with s/n label outside case, OFF/ON switch nearly flush with case, same bridge contact etc.

Version 2b - very similar to Version 3 with s/n inside battery compartment, tall OFF/ON switch, still has bump on 5 key and buggy ROM, but otherwise same as Version 3.

It's the Version 2a that has been used to create fake Red Dots in the past, although it has been stated that there are significant internal differences in construction between a true Version 1 Red Dot and any subsequent versions.

I offer this for academic discussion and otherwise no particular purpose.


It would be interesting for us to track the serial numbers and versions (sort of like megarat has done here for the HP48 series). It would be interesting to provide pictures also.

I would be willing to collect and publish this if others are interested.



Much easier to check are differences between the ser#-labels - but I'm not going to disclose them, sorry. (If you are in doubt, supply a highres-pic to the forum and those knowing will do their judgement...)

The internal parts are different too (and not exchangeable), but one rarely gets pictures of those.


I am well aware of the differences between the serial number label on a Version 1 Red Dot and an early Version 2, and will also not reveal the differences ;). I was merely pointing out that it's the early Version 2, Version 2A if you will, that has been the basis for attempted fakes. My discussion is more oriented towards the variations on the Version 2, and suggestion that perhaps they should be considered two different versions. This would mean that there were five production versions of the HP-35, rather than 4, although the significance of this conclusion is about as important as the position now taken by astronomers that Pluto should no longer be considered a planet.

Edited: 10 Mar 2011, 9:02 a.m.

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