I'd be very concerned about that being a modern forgery, I haven't seen an example with that type of tryzub with a cross on the left side. The srebenniks from this era are extremely rare.
Here is the relevant category at Zeno. All have the tryzub with cross on left but is the condition too good to be true? https://www.zeno.ru/showgallery.php?cat=3392
The tryzub with cross is the tamga of grand prince Sviatoslav (without tryzub it is his father Vladimir). To me the coin looks genuine, but I know this is a very treacheous area with many excellent fakes around. I have the main Russian book on these coins, which lists all types. I'll check it later and come back to it.
I had a look at the book "Monety drevnerusskoi chekanki - konets X - nachalo XI vv." by A. I. Rublev The coin above is a Srebrenik of Svyatopolk Vladimirovich (it is a grand prince I meant when I wrote Sviatoslav above). It is Type II "c imenem Petroc", i.e. "with the name of Petrus". There is apparently no die-identical type in Rublev, but the coin is close to S.2.1.10. Can we know the weight of the coin?
