Uebel is one of those names that is attached to a prominent family, the brothers of which started God knows how many companies. Kind of like how there's a Selmer USA and a Selmer Paris, there's a million distinct brands called Wurlitzer (most prominently the pianos and the high end clarinets...). Similarly, there are several Uebel families that build clarinets. I would think that F. A. Uebel is probably the more noteworthy brand, and I would hold their current clarinets up with the best handmade instruments in the world right now.
G. Rudolph Uebel is no longer a current maker, as far as I'm aware. I don't think their instruments were "lesser" than F. A. Uebel back in the day, they just were a little more conservative in their designs. I have a few G. Rudolph Uebels in my collection, and I am fond of them.
I couldn't really give your instrument a value, as I don't deal in German clarinets often enough right now and I don't know what the Euro market is like, but I would guess (it's only a guess) that you have an upper-intermediate or entry level professional instrument on your hands. And the thing doesn't look too ancient. Make sure you have a barrel and a bell... I don't see one with your pictures, and it might be difficult/expensive to find a properly fitted barrel and bell for the instrument.