Dear Tom! Thanks for the answer. It I am the owner of this coin, I weighed it today on jeweler
scales. Its exact
weight of 4.04 gr. This coin weighs less than about 3.70-3.90 grams if to clean from its surface slag(!).
And these vplavleniye metal it is slag which easily exfoliates from silver!
Besides there in the beginning made trimming of edges of this coin, and then there were these stratifications of slag. And on a coin the double blow is visible, it is made a stamping way.