congratulations.
foreign silver is very hard. most foreign countries with the exception of say canada demonetized their coins long before the U.S. did. so while you occassionally come across foreign coins its rare to find any that have any silver. they have to be quite old like this one.
I find foreign silver on a weekly basis. Would hardly say its rare. Cant remember the dates, but last week I found coins from Guatemala (2), Germany (1), Philippines (1) and Canada (13). All silver. Clad foreigns are much more common, but the silver are just as common as U.S. silver in my neck of the woods. People are filling the handrolls with anything they can find these days.