Good luck with that. Bank managers are quite savvy about silver coinage and most of it goes out of circulation the moment it is deposited. I recall an incident 25 years ago at the bank next door to where I worked. An elderly lady deposited several thousand Morgan silver dollars into her savings account. Someone noticed the transaction and word spead like wildfire up and down the street. Everybody (including me) rushed to the bank to exchange our tens and twenties for "dollar coins". We were all told that the bank had no dollar coins, period. When I was in line you could clearly see them sitting on the counter. I later heard from a bank employee that the bank manager substituted funds from his own account to make good the difference and took the coins for himself.
Stories like yours kill me.
My sister was a bank teller around 1965. Her manager told her to pull all silver coins aside during the days transactions. He would then buy them from her. She knew what/why he was doing that, but she was a college student and couldn’t afford to do the same thing. Dang.