The "torn corner" bit was what made them "unlucky"
Con artist would stack a two and one together. then tear of the corners of both bill, getting the same "tear" line. they they would "paste the 2 onto the one. you only ripped one corner off of each two, and the $2 bill would still be legal tender-- but you eventually ripped all the corners off the $1-- and with a bit of effort and tape, doubled its value. then you took a stack of "2's" with some bogus "2's" between the real ones, went to a busy store, and "bought" something-- so if every 3rd bill was bogus-- you got an $18 item for $15 dollars. With inflation, that is not much of a discount, but in days past-- it was a big deal!
It was done with 20's too, Four corners of a $1 with $20 denomination on it. crumple the bills, put them out of order, it would be easy at christmas time or other busy times to cheat a cashier. which is why they were taught to line up all the bills, face up, in the same direction, and look at the whole bill, not just the corners! Now its easy to cheat credit card companies, and that is not a federal offence...
