[yesbabyyes]

I'm not sure the drop retains half the serial number? GP claims the drop rips the bill in half, and hands the part with the (full, I seem to recall US dollar bills have the serial number on the bottom left) serial number to the courier. The courier can prove they delivered to the right drop, and the bill being ripped in half will ensure it won't be used again.

[RaceWon]

> I seem to recall US dollar bills have the serial number on the bottom left

Our money (US Currency) has two (of the same) serial numbers on each bill; one on the lower left and one on the upper right for dollar bills. Other denominations also have two; one on each side of the front of the bill, however they are in opposite places i.e. upper left, and lower right--at least the current bills in my wallet are that way.