The original Pentax M42 to PK adapters have several different versions. The very earlier version has ASAHI PENTAX marked on top and JAPAN at the bottom, and the marks are in black color. It comes in carton box like this one:
The later version has PENTAX on top and JAPAN at bottom, marks are in either black or white color. It comes in green plastic bag like these:
The original adapters are easy to use, you don't need a tool to take it out of the camera. But I do feel they are abit lose when mounted. Some third party ones are actually better fit than the original ones.
Of course the best M42 to PK adapter (so far I could find) is the one from Kindai:
M42 to PK adapter by Kindai
They are expensive, almost three times as of the original Pentax ones. But if you have some M42 lens from Fujinon (w/ no Auto/Manual switch on the lens), you'd love these adapters.
Last edited by frank; 11-24-2008 at 11:48 AM.