I work at a coin store and becoming a bullion dealer is easy. We may not be melting but coins come in get put in bags and sent out. 90% of the time nobody check for dates and mint marks. Its not that we dont care. Nobody has the time and you almost NEVER find anything of value. Its not like there are just 16-D dimes floating around and 32-S quarters in every roll. As the saying goes there are bigger fish to fry. I ONCE found a 21-D dime in VG while helping a customer look through our junk silver which I ended up getting for $1.20 but other than that we don't find anything.
Im sure this guy makes a lot of money flipping the money fast. Sure you can find something of value but if it sits on the shelf thats dead money and its no good. Flip your money 5-6 times in the time it takes to sell that coin and you've got a pretty nice profit on your hands.