I have been looking around for a crown for my Universal Geneve, and I have found this one: it looks a bit strange for me though, the inside has not the black fill (I don't know how to call it, is it a rubber thing?) and I am not really sure if it is usable in this state? I will be appreciated for your inputs .
It's a gasket, and you need it. A watchmaker might be able to look up the part number, order it, and install it. Are you sure that's authentic? TONS of Chinese replica crowns for many brands are floating around, especially on eBay.
I think even the most venerable watchmaker will have difficulty pulling a part number (less difficult) and original gasket (very difficult) for Universal. Luckily that's not necessary. Most material houses (and some watchmakers) will stock O-rings in a variety of sizes. In this case you just measure and then try a few on until you find one that fits. Vintage pieces are not waterproof--this is just another illustration of why you shouldn't go bath tub diving with your oldies.