you can use any LTM lens using an LTM-M42 plus an M42-K adapter BUT only in extreme close focus area. Remeber the backfocus of Leica LTM/M mount is about 1/3 smaller than M42/ K-mount SLR due to smaller camera width (no need for a mirror).
So with a C/V 15mm your focussing would be probably 2-22mm, at best
When buying a new C/V 15mm you get a Bessa-L for free. It's a greast tool if you like wideangle lenses.

cheers, Frank
http://www.taunusreiter.de/Cameras

Hi Mac,
the f/2 55mm always was a lens to fit the "cheaper" cameras in the Pentax line. i.e. the SP500, SL, SP1000... a marketing issue, bcause besides of missing the 1/1000s, self-timer, TTL or whatever they were the same good cameras for a lot money less, probably the best value for money then.

But don't worry, they are as good as the f/1.8. In fact, some are in fact f/1.8 setting without label that position, or the setting will not hold there. They are capable picture-takers. I've got a 1959 f/2 55mm Auto-Takumar and get tack-sharp negs at 100ASA black&white film at f/8. Never seen sharper ones! Wide open, they are pleasing with color film. Beware of backlight if you don't have a hood.

cheers, Frank
http://www.taunusreiter.de/Cameras/Pentax_Main.html

OK I found it.
Can be seen at:
http://www.taunusreiter.de/Cameras/Pentax_K_engl.html
as well as here:
http://www.taunusreiter.de/Cameras/Pentax_Takumar_Collection.html

cheers

This was one of three standard lenses coming with the 1957' Original Pentax. WTB or WTT

cheers and regards, Frank

http://www.taunusreiter.de/Cameras/Pentax_main.html