Some (most? all?) Nikon cameras allows a 'dumb' flash to fire, no matter what shutter speed you've set it to. Syncing is not guaranteed, but it would be nice if Pentax cameras enabled this (at least as an option in the menus).
Some of the older models (nikon d50, d70, etc) also had some kind of combined mechanical and electrical shutter thing going on. It's been a few years, but they may have had global electronic shutters past a certain shutter speed? I'm not sure, but I recall being able to sync a friend's d50 at 1/1000 using dumb radio triggers and a hot shoe flash still at full power. Depending on the flash power settings, the triggers, and the shutter speed you set, there may be banding. So try out various settings to test the syncing limits before using it for anything important..
Also, nice find