An HP-35 Production Overview

[Didier Lachieze]

(01-17-2022 03:21 PM)KimH Wrote:  What it suggest - maybe stating the obvious here, sorry - is that initially the serial number beginning with YYWW was indeed showing what revision we were dealing with, it did not stay that way.

I can see that on my many Titans, they change YYWW weekly.

Yes the serial number format changed, initially the week WW in the serial number prefix was the first week of the range. This format was used in 1972, 1973 and 1974.

Then in 1975, as I described here, the prefix moved to YYMM, with MM being the Month Manufactured.

It changed again in 1978, I think (but the exact date would need to be confirmed), to YYWW, but this time WW was the week where the unit was manufactured. This format applies to the 41, the Voyagers, Titan and so on until end of the 90's.