Isn't it supposed to be the other way around. You make an offer I can't refuse.. I might have a set, haven't seen them for years. I'll look around tomorrow.
Had a look around. I do have a PK13 but it lives in my case with the 55 3.5 and my F3. When you said extensions (s). I thought of the older K1-5 set. Pre-Ai rings, which I also have in their nice leather case. I'd part with them but I'll hang on to the PK-13.