Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here.
As most of you long time Pentaxians know, I have built a large collection of (mainly) Pentax lenses, from the earliest Takumar M37 lenses for the Asahiflex series through the latest DA lenses for K-mount bodies. My current lens count for various Pentax mounts is 318.
I recently came across (bought on eBay from a Japanese seller, actually) an M37 lens which seems unique. It is the Takumar 55mm f2.2 lens, which was introduced in 1957 in the M42 mount along with the original Pentax bodies which introduced that mount. It was Asahi Optical Co.'s first use of the double Gauss lens design, and was the fastest normal lens available from AOCo when it was introduced.
I can find no mention in the literature of this lens having ever been made in M37 mount, but I'm holding one in my hand as I write this. It bears serial number 179057. The preset aperture mount looks the same as my M42 copy of this lens except that it has an M37 thread. The mount shows no sign of having been cut down from an M42 mount version, and it has all the original DOF markings intact. I suspect that it could be a prototype made at the very end of the Asahiflex era to evaluate the new lens design before the Pentax bodies were introduced, but of course I have no way of proving this.
I'd like to ask of you who are into Pentax esoterica and history to tell me anything you might know about this lens. To reach a broader audience I'm also posting this message in the DPR Pentax SLR forum. Thanks in advance for any light you can shed on the history of this lens!
Regards, Jim