Postby Qrt.S » Thu May 14, 2020 9:24 am
madej is right, it is Warsaw in Poland and the assayer OC is very well known Osip Sosnkovsky 1862-1896. He is also known as Josef Stanislavovich S., marking IS 1852-53 and Ios S. marking IS 1850-1862.
Sosnkovsky never worked in MInsk in Belarus. This is a common misunderstanding related to the Minsk chapter in Postnikova on pages 200-201. It is a complete mess. Most of the names worked in Warsaw. Riedel is also incorrectly placed in Minsk as #1906. Minsk and Warsaw town marks are very similar, both a double headed eagle. This probably misled Postnikova, who knows?