HP-35 Serial Number Question

[Corvallis Bill]

Hi,
I have the 35 with a raised bump on the "5" button, signifying it is rather early in its evolution.
The ser no is 1143A 41k and from what I read, that indicates it was manufactured in 1971, in the US.
So far, all of the articles I've read about this series says they were "first released in 1972", so my question is why wouldn't this one be serialized with the 1200xxxxx designation? Was it an earlier production unit?
I know there are others with the 1143A ser no so wouldn't it then stand to reason that the first release would have been in 1971..? Any historians out there with the answer..??
Thanks..Bill (a.k.a. Corvallis Bill).

[teenix]

There are a few HP-35 serial numbers with 1143 listed in Collectors Corner.

It is fairly late in the year, so (guessing) maybe these have been manufactured in 71 and released in 72.

cheers

Tony

[Didier Lachieze]

The 1143A comes likely from the first pre-production units built end of 1971 before the official HP-35 launch date on January 4, 1972.

This date code was not changed every week but only when significant changes occurred in production (the next one was 1230A), or when reaching the end of the 5-digit serial number within the range.

See An HP-35 Production Overview for more details.

Note: looking through my HP-35 database a 1143A 41k unit was likely built beginning of August 1972.

[Corvallis Bill]

Dieder,

Shouldn't the ser no for a unit built in 1972 then be 1242xxxx and not 1142 then..?

Thanks for all of the replies. I'll check the quoted links.

-Bill

[Corvallis Bill]

I get it now...

The 1143A held on from the first production release design into 1972 and only changed to 1230A when there was the next design change and also released in 1972.

So the calculator I have with the 1143A 41k I can understand why it was manufactured mid-1973, as Dieter states but does still retain those first production run characteristics.

Since my unit has the raised 5 key can I presume it has some historic value in the evolution, compared to the more common 1230A..??

Thanks Guys...!

[Didier Lachieze]

All production changes didn't drive a date code change (for example with the removal of the famous red dot the date code remained 1143A), so there is generally not a direct link between a specific date code range and specific features sought after by collectors.

You're right in saying that the raised 5 key has historic value as it is present only on the early HP-35 units, this removal happened in January 1973 around the SN 1249A10000 and was not a sharp transition as there is a mix of units with and without raised 5 key between 1249A10000 and 1249A11500. This means that all 1143A, 1230A and most of 1249A plus part of 1143S were produced with the raised 5 key which represents roughly 80k units or ~23% of all HP-35 units.

[Corvallis Bill]

Thanks Didier,

I understand this better now and the fact that back then, the date coding of consumer goods didn't mean as much as for military hardware...traceability on a calculator probably wasn't a thought at those times.

Well, I'm satisfied that the unit I have has a bit more value to me than the later, more bountiful 1230A's...After I get it and clean it up, it'll be nice to see it on my desk.

Glad this Forum exists and I'll keep reading things as I need to (I also have a nice condition used 65 and 41CV). I purchased a 45 back when they first were released and I was in engineering college at that time. Worst mistake I made was eBaying it many years ago, when I realized I no longer used it. Many years after that, I wished I had not have sold it off. Did the same with a new 41CV in the 90's and regret that too.

Regards,
Bill