Originally posted by RKKS08 Is it a M42 or PK version?
I don't know this lens, but if M42, it's most likely an East German lens from the late sixties.
In the late seventies, Porst switched from M42 to K-Bayonet (for a while) and sold Cosina made Pentax-M series clones. The lenses were mostly rebadged Japanese lenses from many different manufacturers.
EDIT: In the sixties, they also sold cameras and lenses made by not so well known West German manufacturers (Balda, Isco, and others) under the Porst name. Unfortunately, none of this gives a hint about quality. All of them made some outstanding things, and a lot of crap, too.
I have bought a lens because I could find someone who had it previously, and sang operas about its quality. At least we know now.
I am really curious!