Somewhere I worked used the wrong serial numbers of postal delivery. We had an overflow which no one noticed for about a year and we ended up using the same ran

Somewhere I worked used the wrong serial numbers of postal delivery. We had an overflow which no one noticed for about a year and we ended up using the same range as another customer of the postal company. There were thousands of parcels with duplicated serials, everything arrived fine and as far as I know there's been no real admin issues either. So in this case it didn't matter.