Originally Posted by Miserere 
I have a Jupiter-9, but it doesn't seem to be that uncommon, at least amongst Pentaxians. One lens I have that I haven't heard anyone mention is the Toyo 28mm f/2.8. It's a tiny (like the FA 50, but lighter), unassuming lens that delivers impressive pictures. It spent a few months as my walk-around lens on the K10D and it served me well. Here's the lens itself:
Pretty little lens and great pictures. The appearance of your Toyo reminds me of the Prinz Rexatar 50mm that I owned during the 70's.
Steve