Nesster,
you started it with a non-Pentax lens and camera, so I'll not be too ashamed for this: This is one lens that still waits for conversion onto PK-mount. Scientists from all over the world are undecided wether this is possible ;-) It is Praktika-B-mount which could be squeezed somehow into PK (handheld scientific test :-) If I could only make up for the 1.1mm difference in register.
Ladies and gents, you see here the first version of this lens (outer barrel engraving), which is a nothing else but a multicoated
1.4/50 Pancolar (drooling and moaning from the audience). I've
disassembled this lens to the bone (blades) and got it back together :-) All these first version series have yellowed glass. The second version (inner engraving) however is not yellowed but a different lens scheme and comparable to an ordinary Takumar (crowd gets raucous and menacing, quick exit of lecturer).
All the best, Georg (the other)