Just found out there are actually valuable old American bills still floating around that you might stumble upon. Like, there's this massive $1,000 bill from way back that could be worth $1,500-$2,500 depending on condition. Then there's the 1928 $500 bill with McKinley's face — that's worth around $1,000-$1,500. Even a 1950 $100 bill with Benjamin Franklin can fetch $120-$150 if it's in decent shape. The rarest ones are those 1933-34 $10 Silver Certificates with the blue seal — light green seal versions go for $20-$35. Obviously you probably won't find these in your wallet, but apparently collectors are seriously hunting for them. Makes you wonder if any of these are actually still in circulation somewhere. Wild that some of the largest denomination bills ever printed are technically still out there. Have you ever come across any old bills worth checking?