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HP Forum Archive 16

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Help...HP-35 Red Dot????
Message #1 Posted by cipo on 16 Jan 2007, 11:13 a.m.

Hi All,

I need your help in finding more information about a calculator I found while moving into a new place. I am an engineer myself so very curious about this thing. From what I got so far it is a HP-35 Red Dot version 1. This is rare right??? Can someone confirm that it is a Red Dot from my pics link?

How much is this thing worth??? What should I do it it???

It come complete with: molded case operating manual AC adaptor Waranty Information/Shipping/Accessory order forms

There is a few things wrong: Battery is dead, and either the on/off switch or connector is lose so you get intermitent power depend on how you hold the calculator.

All LED are working and calculation are functional. Serial is unknown: Look like this... 1143A XXXX1 (where in the X are faded unreadable character...looks like 0???)


Re: Help...HP-35 Red Dot????
Message #2 Posted by Les Wright on 16 Jan 2007, 12:05 p.m.,
in response to message #1 by cipo

I believe you have stumbled on an early red dot production model manufactured in 1971 (60 + the first two digits of the serial is the rule).

Here is a pic of the model from this very site.

I believe it is quite valuable on the open market, but not as much the prototype model with yellow keys.

Replacement batteries and AC adapters are readily found. eBay seller waterhosko sells suitable handbuilt NiCads for $12 a piece. The AC adapter is the exact same one used by the HP45, 65, and 67, which are later and much more common models. I have one each of those calculators, which means I have technically two extra adapters!

The fact the display works and you can calculate is very good indeed. If you are serious about refurbishing this thing to the best possible condition I recommend Randy at


Edited: 16 Jan 2007, 12:06 p.m.

Re: Help...HP-35 Red Dot????
Message #3 Posted by Massimo Gnerucci (Italy) on 16 Jan 2007, 12:33 p.m.,
in response to message #1 by cipo

Yes it is!
Two color manual, rear external narrow S/N label, no model # and, finally, red dot are consistent with rev. 1 of the HP-35.
Congratulations! You've got a rare bird...


Congratulations! (NT)
Message #4 Posted by Walter B on 16 Jan 2007, 3:25 p.m.,
in response to message #1 by cipo


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