@ QRT.S: thank you very much for your kind answer. This item does not belong to me, I have unfortunately only one picture of the stamp. Perhaps I get still another picture of the whole piece. It is 2 kg heavily and from a very good quality, probably also very old. Nobody would make itself today the work to falsify such a thing. Helmet from silver, covered with cloisonne email, in the back long chains from silver such as hair. Surely a traditional costume. I can imagine that the piece comes from Turkmenistan or Uzbekistan, perhaps from there the similarity to the Russian hallmark. But only an assumption, I am no expert here, so my question in this forum.
(admin edit - see Posting Requirements ) Kind regards Steffen
P.S.: Have not forgotten the hallmarks on the Cloisonne-Box, but had still no time, sorry.