The answer to your first question would be considered exposure if it did or didn't use a shell so I'm sure you understand why I can't answer that
Homer used Morgan silver dollar coins in the demo.
Most coins like this are available privately from sellers or coin shops that sell rare or old coins. I got my set from a coin shop although I hear gun shows sometime sell them.
Shells are available for almost any kind of coin you can think of. Some coin makers even make gaffs out of the coins you already have.