Yep. It's the wrong kind of ligature, that's for sure. Old German clarinets would normally use a harder, stiffer reed, which would be tied on with string. That metal ligature is standard for Boehm system clarinets. The German mouthpiece will also have a different "lay". The lay is the size, shape and curvature of the opening. I'd guess it's a matching mouthpiece, as they aren't made of boxwood anymore, either, and the lay looks to be pretty small, which would befit a German reed. Believe it or not, today's best mouthpieces are made of hard rubber!
On another note, the barrel (the piece right below the mouthpiece) looks to have a crack running it's entire length, and even down the body of the clarinet. I can't tell if it's been repaired, and if it has, I can't tell if they did it correctly without having it in my hands. (Can you tell I used to repair clarinets? I've got a few in my collection of instruments so far as well.)
While these cracks anything to be alarmed about, I would suggest (for posterity's sake), that you keep the clarinet away from the heaters and open windows. Ideally, it would be somewhere with a 40-60% humidity level and at room temperature. Don't worry about fixing them unless you plan to play the clarinet, or if you want it to look original. Doing any work at this point, could end up damaging it more, and regardless of it's monetary value, I'd hate to see anything of it's age be damaged anyway. I doubt that it has a metal lining in the barrel, but some old wooden clarinets did, as did many wooden flutes, and unfortunately, wood and metal expanded at different rates, so the barrels were almost guaranteed to crack.
Quite a nice piece of history you've got there. Can you tell this is my other passion? LOL