The cut oval frame with a workers head is a Soviet import mark for foreign objects presented by customs in a Soviet assay office in Tbilisi (O). It was used 1947 to around 1954. Unfortunately I don't know the other mark but it is obviously the maker's mark in the exporting country? The 875 is the silver fineness in promille (former 84 zol.)
Guessing a rising sun/un soleil levant over HS for Henri Soufflot 1884/1910.
Then Soviet mark for foreign made silver after 1927 (worker`s head in profile with hammer). Assay office looks like Hellenic letter omicron for Tbilisi.
Regards
No one seems to have noticed that the Minerva hallmark is very rough and the details indistinct. This is indicative of an object that has been copied from another, making a mould from the original and then casting copies.
In such cases, the hallmark, instead of being sharp, has exactly the same rough, grainy look as the rest of the object. And even if the object is polished, roughness will remain inside the hallmark. Look at the brush at the top of Minerva's helmet, no bristles are distinct.