Hello there Ca-anton,
How's your German? Good, I hope - most of the market for Ury is in Germany. ;-)
I don't know much about Lesser Ury, but his work is still actively sold at auctions, and for quite nice prices, too. If that's an original (which to my untrained eye it might well be), then it's going to be worth spending some money to find out.
I would start by going through some of the big auction web sites like Artnet, and making a note of which auction houses have sold several pieces of his work, then Googling them to get contact details. Finally, send out an e-mail or two to gauge their interest/price for looking more deeply.
Take some very clear photos of the work, including the back (you'll want to carefully open the back of the frame if you haven't already) and the signature. Get some up-close photos of the texture of the paint. Appraisers will want those, and others I haven't thought of.
A good starting point might be Ketterer Kunst, which claims to have sold over 30 works by Ury, and has one on offer now for over $20,000.
http://www.kettererkunst.com/bio/Lesser … 1931.shtml
Please let us know what you find out, and if you're willing to share your experience of finding an appraiser and going through the process, it will educate our community.
Best of luck,
In my short search, I found the