Straight Edges
Straight edges on the bill stamps are very unusual. They were not planned but were the result of misalignment when the sheets were fed into the perforating machine.
Very little selvage is left on the right hand side of the stamp after perforating. Any misalignment in the sheet when fed through the perforator would result in the last row of pins missing the stamp.
The bottom row of perforations are missing on the 3¢ value above.
This is very unusual having a straight edge on the left side of the stamp. The 6¢ value above was trimmed removing the selvage and counter from the sheet.
Varieties
Straight Edges