Here's a close up of the arms as requested. It is indeed those of Dolgorukov and they were an ancient Princely family. Catherine Dolgorukova was the Mistress of Alexander II.
I don't have a photo of the rear of the mirror I'm afraid as it's not with me at the moment after I took these photos the other day. The arms however are not soldered to the mirror as there is some movement in them.
I understand that there are indeed a lot of fakes about these days, and a lot of new Russian silverware passed off as old, or just "in the manner of" with spurious marks.
I should point out however that this piece was purchased by my parents for their antique business well over 20 years ago now, and although there may well have been fakes at that time being made, there were far fewer than there are nowadays. My mother can't recall for certain, but it's possible that the mirror was purchased from Christies along with two very large trunks which previously belonged to Maria Maximillianovna Romanovskaya who's provenance was without doubt.
I've also confirmed that the arms depicted on the Wiki page actually have errors with regards to the direction the eagle faces, the angel and also the curtains overlapping one another. A correct depiction of the arms can be seen here
https://picryl.com/media/coat-of-arms-o ... 798-364166
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