I admit, I did shoot it years ago. I noticed the firing pin and haven't shot it since. I hadn't thought about the firing pin getting stuck, good point.
I don't know much about these, but have seen pictures of 1916 Erfurts on auction, with a little info on them. I wish I knew more.
I'll have to double check the mags, I don't remember seeing a serial number on them.
Regarding the serial number, I remember seeing something about 1-10000 and then a1-a10000 or something like that. This one doesn't have a letter prefix that I could find. I'll see if I can do some more research on it.