At a certain point during production one of the perforating wheels became
defective. In the course of repairs part of one perforation wheel was
inadvertently changed from Perf 11 to Perf 10. Based on the physical evidence of
surviving copies, this was the nineteenth row of pins on the wheel.
Many examples of the Perf 10 on One Side rarities show transitional perfs from
10 to 11 or from 11 to 10. This is because the out-of-gauge perforation pins
would frequently cross the span of more than one stamp, depending on where the
wheel contacted the sheet.
The Perf 10 on One Side varieties span both the 1917 Washington-Franklin and
1922-23 Issues. It is interesting to note that, apart from the 2c, there is no
duplication of denomination between the issues. This would seem to indicate that
the improperly repaired wheel was in use for only a short period of time, as
there was little overlap in production of the issues. Based on dates of issue of
the basic stamps, this probably occurred early in 1923.
This census lists
only the used copies. Approximately twelve unused are also known (including two
in a block of four, four in a block of 25 and and two in a plate block of six).