The short answer is - It All Depends.
If grandma drops off 1000 face in pure silver dimes, then you would be getting 100% silver dimes.
if timzim starts doing dimes, and you buy his dumps, you will get about 50,000 dollars worth of skunks, before you even have a chance.
It doesn't matter - you just have to do volume. Personally - I would go to many different bank, and buy all the "customer rolled dimed" you can find.
I do alright - somtimes 2 silvers in 20 bucks. sometimes Zero silver in 300 bucks.
I get more dimes from teller trays through, cause I always look!