Kassel was an interesting place, a major depot was there during WW1 and WW2 - up until 1926-28 (can't exactly remember) it was spelled Cassel, and was changed to Kassel - no idea why. But, you can find WW1 and interwar Gew.98 rifles marked Cl on the wrist, and later Kl. It seems that Lugers weren't reworked all that much, which makes sense because pistols generally don't see a lot of hard use. Many of the reworks I see are conversions from Artillery models, but my observations could be skewed because I don't research Lugers too deeply, I was just wanting a marked rework variant.
Anyway, the Kl and date of 1933 fits with the Kassel theme. It's interesting that the top of the chamber was the preferred real estate for marking them as repaired, just like the SS did with the deaths head Lugers. I'm sure it would be an interesting subject, but I can tell you from experience many in the other collecting fields (not singling any specific one out) don't avail themselves to non-community members theories and ideas, so if you do figure something out expect it to be largely dismissed or accepted with tepid interest.
