HP28S production years?


The museum pages give the following information on the production dates of 28C and 28S: "Production Runs: HP-28C: 1987-1988, HP-28S: 1988-1992". Yet I have a 28S which has the year 1986 marked on the back cover. Which is correct, any ideas? Is that just the design date of the plastic cover, which is probably the same as in 28C...?


Having a look at my HP28S, made in 1990, I read

IMHO that means that the Copyright for this calculator (i.e. patents etc.) was claimed in 1986, just before the first production run of the 28C series.

Greetings from Hamburg,


Hello, another question : I have an 1BB HP28S, is that normal ? Thought all 'S' were 1CC.


I've been rather under the impression that all 28Ses were 2BB, and 28Cs were either 1BB or 1CC.



Thank you, I will double-check but am sure it is an 1xx version.
That's strange. The serial number seems to have been wiped with a soldering iron. And -before you ask- no, I have not stolen this machine :-)

By the way, today I saw a prototype HP40G with 1.32 ROM version, and a sticker on the back stating (roughly) "Prototype version, to switch between 39G and 40G press F2 then ON, then ON+F3".

I guess there are a number of prototypes around.


Yes, it could be a prototype; maybe a leftover circuit board with an old 1BB RAM stuck into a 28S case? How much RAM does it have? How does the lettering above the keys compare with the Museum photographs?

Also, on the back, near the serial number, my 28C has that weird symbol to the left, and "COMPLIES WITH THE LIMITS FOR A CLASS B COMPUTING DEVICE PURSUANT TO SUBPART J OF PART 15 OF FCC RULES" "ATI conforms classe B" "MADE IN USA".

On my 28S, the strange symbol is to the right, and the text is just "(c) HEWLETT-PACKARD CO. 1986" "MADE IN USA".



Sorry, it is a 2BB. Thank you.


That makes sense, thanks Ralf! Now of course I still don't know which year my 28S was manufactured, but that's another question...
Cheers from Helsinki,


On most HP calculators, you can find the year of manufacture by taking the first 2 digits of the serial number and adding 1960. For example, my HP-42S has a serial number starting with 33, so it was made in 1993.

There's more information about serial numbers here.

- Thomas

Edited: 22 Sept 2006, 7:21 a.m.

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