Actually, in the late 1860's the Philly mint began serving the public as a clearinghouse for dirty coins. About 60 million coins were turned in, 35 million cleaned and sent back out, while 24 million disappeared into treasury vaults. 91,000 were documented as melted. Figures for coins redeemed prior to 1871 are not available.
We should also make a distinction when talking about surviving populations with regard to survivors that a collector would want to have. Zillions (actual count!) of the early year shield nickels are too corroded/damaged to be reasonable studied in the attempt to build a decent collection.