Does someone know how to tell is this coin deliberately blanked from the back or might be factory error?
Written on the coin in Russian: чистаго серебра 4 золотн 21 доля
Similar coin with both sides:
https://www.raritetus.ru/stoimost-monet/carskie-monety/aleksandr-i/serebro/1-rubl-1810-spb-fg-11179/
My coin: