First Russian Kokoshnik Stamp 1899-1904

I have researched over a year trying to find who AB is.
Romanov Russian Jewelry has a piece with the same marks and they stated AB is for Kiev assay master Alexander Vyrzhikovsky 1899-1904. The other stamp I believe is an M in Cyrillic alphabet and I think that is an X but the lower part is worn, so I’m not sure. I know the 56 is 14k and AB is, I believe, Alexander Vyrzhikovsky. Can someone help me? I want to be sure the above is correct. Any help would be greatly appreciated.