About HP calc serial numbers



This page: http://www.finseth.com/hpdata/serial.php explains that the week number in HP calculator serial numbers starts from Nov 1st (HP's fiscal year start).

So, then if I have a calculator with the serial number of 2205Axxxx this would mean it was manufactured in 1981 December, right?

Or have I misunderstood something?


Regards, Ernst


I'm not sure if this is an "urban legend" or correct at all. Maybe someone can prove or disprove this quoting a reliable source.

But: The earlier machines had something that I would rather call a "batch date" or maybe "revision" date. The 35 started with a "1143" datecode, next in line was, AFAIR, "7230".

So the given explanation of serial# is, at least, partly wrong.


Traditionally HP used the first four digits for the year and date of the start of production of a specific revision level of a product. They might make products with a particular code for a long time, not even just one "batch", if there were no design changes. Those first four digits were what you looked up in the service manual for "back-dating".

Calculators started out that way, but quickly became the highest-volume HP product, such that the standard HP serial numbering scheme was not practical. For calculators, they decided to change the code every week, even if no design change had been made.

There were occasional errors or anomalies in the serial numbering. The serial number of the calculator was not particularly intended to be interpreted by anyone other than HP.


I purchased a new HP-15C in December 1985 from a large-volume dealer. The serial number on it is 2605A02499.

I've owned HPs since the mid-1970s, so I was familiar with the significance of the first five characters of HP serial numbers of that era. I was surprised at that time to see an early 1986 serial number on a device purchased in late 1985.

This one example supports the statement that the serial number year began late in the previous calendar year.

Edited: 27 Jan 2011, 10:40 a.m.

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