Serial numbers format question

[Didier Lachieze]

I was looking at the HP 29C Service Manual when I noticed something unusual regarding the serial number format.

HP calculators serial numbers from the HP 35 to the Pioneers and 48 family are documented on the hpmuseum (Decoding Serial Numbers) as following the format below:

Code:

Numbers are in the format YYWWC##### where 
YY     Is the number of years since 1960. 
WW     Is the week (roughly) in which the unit was made. YYWW is not always exact 
       and sometimes may have gone weeks or months without changing. 
C      Is the country code: A = America (USA), B = Brazil, G = Germany, J = Japan, 
       S = Singapore, M = Malaysia or Indonesia. 
#####  The serial number within the specified week and year.

However, in the HP 29C Service Manual, the serial number format documented is YYMMC#####.

Note the MM (Month Manufactured) instead of WW for the week.

I did a quick check on my calculators and the ones I could find on-line, and indeed I noticed that:

• In 1971, 1972, 1973 and 1974 the serial numbers include non-consecutive Week numbers (up to 50 for the HP 45: 1350A#####)
• In 1975, 1976 and 1977 the serial numbers seem to include the Manufactured Month documented in the 29C Service Manual, as the MMs I've found are all between 01 and 12
• In 1978 and beyond the serial numbers go back to include a Week number after the two digits for the Year with WW greater than 12.
  

So I would like to ask you some help to confirm the serial number format used in 1975, 1976 and 1977: do you have any HP calculator in your collection with a serial number starting by 15, 16 or 17 and with the 2 following digits greater than 12, indicating it could be a week number rather than a month number?