Paul C was likely the original (German) owner of the holster. The Feb 1945 date is hand-written American-style (particularly the 1 is the giveaway here), so I think the town name goes with that and denotes where the new American owner acquired it. Blatzheim is located in the far western part of Germany between Aachen and Cologne, about where the advancing US forces would have been in February 1945.
Just supposition, of course, but I'm pretty sure that's it.