Most of these lenses should provide good performance though they were all "off-brand" lenses when they were made by various Japanese optical houses. The pricing, though is nothing special and seems a little on the high side to me. (Hard to say since the market in Europe is different than the US.) For example, the XR Rikenon 50/1.7, while a good lens, can usually be purchased on *Bay for less than $50 USD. That is half what the seller is asking. The same is true of the Chinon 50/1.7 which generally would be valued less than the Rikenon.
In terms of desirable items. The Revuenon and Porst f/1.2 lenses are rumored to be the same product under different names. Both are "cult classics" and regularly command fairly high prices though 400+ Euros seems very steep to me. There is a review of this lens in the third-party lens database of this site (
Click here for review).
Link to *Bay auction for a Porst 50/1.2
http://cgi.ebay.com/Porst-Fujica-1-2...d=p3286.c0.m14 (caution...Fujica X mount, not Pentax K)
Steve