It is fairly common.
The stamp 'set' were roller dials in a row so they could be spun to the numbers needed at will.
As the rollers wore, or if one broke, they could replace the bad roller.
If a stamp was deemed bad enough, they could also grab a second stamp set & tray again.
Some interesting sets of various stamps & other examples can be seen at
The 1970 Hamtramck Registry "Factory Errors (Pg. 1)" Page
