When I was 20 I worked at a video game room at the Mall, so you'd have these grandmothers giving their grandkids bags of silver quarters and once in a while you'd find confederate dollars.
Also, at night when we'd cash out the money we exchanged that day id have to run 500-900$ worth of quarters thru a counter. Silver quarters make a rather distinct sound when they go thru the machine so id just stop and find it. I probably had a few hundred dollars in just silver coins by themselves, much less the confederate $1 and $5 bills with the red lettering on them.