OK, before I start guessing(and I will shortly) the best thing you can do is go see Hemmerle Jewelry over in Munchen. They were started in the 1800's by two brothers and designed for the Bavarian Court. I am quite sure they can tell you all about your brooch. Their website is www.hemmerle.com and you have your choice of german or english to use. They can look at the marks, the stones, the quality and so forth. This place is one of the best anywhere. NOW, I think the piece is Russian or possibly Franch, but I lean heavily toward Russia. If those stones are real, then I think this is a custom made piece, possibly a gift for someone special. The use of silver instead of gold would indicate that somebody wanted quality and to save a bit of money although it was not unusual for jewelers to work in silver too. It may just be for a special person(what was the Aunt's name?, or even for royalty. It is a magnificent piece of work. I say this because during the U.S. depression(1929-1940 or so), my grandfather in the early 1930's sold Pierce Arrow autos(to very rich people). He took a ring as a down payment and gave it to my mother. It was a custom made replica of the Eiffel Tower done in platinum and diamonds. Very large, very spectacular and very similar to your workmanship. Your brooch is very unique and VERY beautiful. Hope this helps and congratulations on such a fine treasure...