I found this Argus C3 Matchmatic lens in the Freebie stuff at the Argus Collectors Group annual Gathering, Eden, NC, in 2011.
50mm f/3.5, made sometime between 1958 and 1966, intended for an Argus Matchmatic C3 camera (the one that is sometimes referred to as the "Harry Potter Camera" groan groan). The lens is a fairly simple Cooke Triplet design, and the glass is coated.
This week I finally found a good project for it, (partly inspired by something that Joe Smith, ACG friend from Haliburton, Canada, did with a C3 lens and an Olympus digital body).
I cut a hole in a Pentax K Mount body cap, removed the geared rangefinder coupling collar from the Argus lens, and installed the Argus lens mount into the Pentax cap.
The lens to image plane registration distance is rather different between a Pentax SLR body and an Argus C3 body, so it will not focus to infinity. With the lens installed into the cap as far back as possible, range of focus is limited to bwteen 13 inches and 27 inches, measured from subject plane to image plane.
I decided it would work well as a dedicated close focus / macro lens and it can fit any Pentax K mount body, whether film or digital.
Initial test showed that the K100 D body's meter would not expose accurately, but this was quickly overcome by dialing in one full stop of exposure compensation.
Today I took the K100 D with Argus lens for a little walk around the studio and yard.

The Argus lens exceeded my expectations.

Please click on images to see enlarged.
All images are ©2012 E.J.Kowalski.