In Flea Markets, you have to go straight to their 'sale' section or box where they put all their extra coins. I have gotten a good amount of coins that way. Its really cool.
A roll of dateless buffalo's goes for $7-$10 any given time on Ebay, I'd say you did fine. 2 weeks in white vinegar for me has brought out about 5 out of 12 dates, 1916 (2), 1920,1924,1934