In my records the assayer Ivan Tschertenkov (ИЧ) was in Minsk in 1878. The town mark of Minsk is often mixed with Warsaw's town mark. Unfortunately the maker Schneidman is unknown to me.
This is not Minsk. This is Kamenetz-Podolskiy (Каменец-Подольский). The town marks of these towns are similar. Ivan Tschertenkov (Иван Чертенков) worked in Kamenetz-Podolskiy in 1866-1883 and never worked in Minsk.