Thank's again for your remarks. As you probably understand, I'm very much an amateur in this field. By saying mirror image, I mean that in the link above the "U-like" mark is pictured as wide on the left side, thinner and narrowing from the right side. I do not know how much this varies within one mark, but on my piece of jewellery it seems like it's opposite: Wide on the right side, thinner and narrowing from the left side.
Would a better photo make it easier to decipher the makers mark, and would it be likely that one could identify this maker? I'm really interested in the history of this piece. Is there something special about Kazan or filigree from there for example, even if the maker is unknown. (admin edit - see Posting Requirements )
Once again, thank you for your time answering me.