I also took some test shoots with them, using the same settings on my Pentax K-x and SMC Pentax-A Macro 1:2.8 50mm lens. In my eyes, the images through the Kalimar adapter (the top two) are better in terms of resolution. What do you think?
Both adapters are safe to mount on Pentax AF bodies although the mark "KAR" (for Pentax KA and Ricoh P) on the Kalimar is more proper.
I have a separate post for the Sears Auto 2X Tele Converter.