The User's Review: 2 Auto Sears 50mm F2 Prime Lenses, Made by Ricoh in Japan
I have these lenses with PK mount in hands, and find that they are the same in all aspects except the barrel length. Their glass formula, aperture ring and blade (6 pieces) are the same. Besides with a narrower focus ring, the smaller lens was achieved by cutting the length of parts beyond the front element.
These two lenses should be made by Ricoh for Sears.