I found this little uncirculated $20 orphan while searching through some notes. Still quite miffed as to how this serial number could be printed.
As you can see from the scan below, the first set of serial numbers are normal. As for the second set, you can see that the '0' has been shifted up from the fixed alignment of the serial numbers.
Now, with most serial number errors that you would encounter, most occur when the numbering device did no rotate completely to the next number or became stuck partially rotated, such as a half of a zero, etc. However, with this particular error, the full zero is printed very clearly and out of the straight alignment.
I am still unsure how this could occur, especially when the '0' is a fully printed.
Any thoughts?