I bought $6.50 from a bank that has only produced one 64' and 1-2 40% halves in 40+ visits. The teller says "there's no silver in these." I said "I check for error coins etc so I am not worried about silver." Theres a grimy 68 right in the handful standing out to me. The tellers at this branch seem to not inspect the edges and only look for 64' and before.
For the 90% I scored there a few months ago I asked the teller if she had any halves, she said "yes but it is someone's $500 that had already been searched for silver." I asked if she had any loose ones and she said "yes, but only one silver one." I said fine I'll take what loose ones you have" and bought $50 of the dump for a piece of mind. There was nothing in the dump of course. She was perfectly willing to give me only the 90% one which she threw in with the rest of the loose coins in my envelope. I thanked her profusely. The other tellers were heated because I assume they keep their silver but the woman was sort of saying to the others -look I know what's up but want to give this guy the coin. I always try to get her window otherwise this bank doesn't produce. Moral of the story, don't give up. Over time you may win a teller over with persistence. I try to only go every other week at most so I don't bother anyone but I can tell most branches are like " nothing new since last month". LOng story short, the teller tray scores are sweet, especially if you don't buy all the dumps to get it.
About 3 years ago my bank called me to come in as they had some silver quarters for me. When I got there they sold me a FULL ROLL of silver quarters for $10. I bought them 2 dozen doughnuts