OK, I sat down with the "The Ultimate Asahi Pentax Screwmount Guide" and the serial number data from m-fortytwo.info and hashed out some serial number/date correspondances.
The method used was this: determine the year of introduction of a lens, determine the lowest attested serial number for this lens, assume that that the serial numbers had progressed to said number by said year. This assumes the following: 1) serial numbers are unique. As I understand it, there is no evidence that this in not true. 2) while Asahi may have produced lenses in batches, serial numbers were in general used sequentially. 3) Gerjan's dates of introduction are correct. 4) m-fortytwo.info's serial numbers are correct. Most of them are Gerjan's! I expect some errors exist in the database either from typographical errors or misidentification of exact lens models. 5) the lens serial numbers are original, not changed by replacement of parts for repair or deliberate forgery. Note that this doesn't say anything about dates of sale. Stuff could have sat around a while in some dark corner before actually entering the market or the field. serial # 546014 was in use by 1958 (interpolation puts serial # 600000 in use by 1961) serial # 677842 was in use by 1963 serial # 732001 was in use by 1965 serial # 2241359 was in use by 1967 (big jump!) serial # 3435021 was in use by 1968 serial # 4188173 was in use by 1971 serial # 4635057 was in use by 1972 (interpolation puts serial # 5500000 in use by 1973) serial # 6872336 was in use by 1974 serial # 7370589 was in use by 1974 I suspect that slightly lower numbers were in fact in use by any given year, given that it seems unlikely that the several thousand entries in the database have captured the first production batch of every lens when over 7 million lenses were made. Also, I'd expect Japanese availibility of many of the lenses to be a little earlier than for Europe/America, and I assume fewer of the Japanese-market lenses made it into the database. My underlying interest in the whole chronology thing is that I was born in January of 1969. I was sure that I had a couple of lenses with serial numbers around the 1,000,000 mark that were older than I am because the lenses were discontinued before 1969. In fact it appears that serial number 1,000,000 was probably issued in 1965 or 1966. It looks very likely that any lens with a serial number less than 3,500,000 is older than I am--this includes almost all my Takumars and Super Takumars, pretty much my entire pre-SMC kit! DJE
