Originally Posted by Martin Bull

The half-track looks like a SdKfz 10/4 mounting a standard 2cm Flak 30. This weapon had a practical rate-of-fire of 120rpm and was replaced by the Flak 38 which was broadly similar but had a much increased rate ( to 220 rpm ). Vehicle and gun were both well obsolete by the time of Arnhem but of course, all sorts of weird and wonderful things were pressed into service to meet the airborne threat.

I can't find a projectile weight ( even though I have a deact 2cm Flak round right here next to me... )

The photos aren't credited, but looking at the shot of the half-track I get a distinct feeling that I've seen it somewhere in a newsreel - could it be a 'still'.....?