I worked as a part-time bank teller from age 1999-2007 (not continuously). Over that time the volume of silver certificates and other special currency coming in dropped DRAMATICALLY. From 1999-2003 I'd say I would see those bills come in about every other month; I don't think I saw a single one in the final two years I worked the job.

I "purchased" (i.e., exchanged my own money for) every bill and coin that came in. And before anyone makes any assumptions, I had permission from the bank manager.