Some web sites dealing with Pentax equipment.
Bojidar Dimitrov's Pentax K-Mount Page is a very thorough and detailed source of information about every piece of Pentax K-mount hardware imaginable. The problem is that the information stops at the *ist film camera. Apparently, this site was in jepaordy of being shut down by Mr. Dimitrov, but the hue and cry of his fans has purchased a reprieve. He says he's going to start updating the information and adding new entries, but it'll likely be slow going.