The offset method, found only on the perf 11 and imperforate stamps, can be one of five types, Type IV, V, Va, VI, or VII. It may be helpful to remember that only offset stamps can be types IV-VII and only types IV-VII are found on offset stamps. Types I-III are found on flat plate and rotary stamps. It may also be helpful to remember that the imperforate offset stamps follow the same type designations and numbering sequence as the perf 11 offset stamps. Many of these stamps were privately perforated by the Mailometer Company using the Schermack Type III perforations.
|Type||Perf 11 US Number||Imperforate US Number|
Any of the imperforate stamps can be manufactured from the perf 11 stamps by trimming the perforations, although the resulting stamp will appear a little small. The two dangerous fakes in this group are the type V and type VII. Both can be manufactured by altering the Va design.
In general, care should be taken when examining the offset stamps, but in particular with imperforate singles. Many of the imperforate sheets were given perforations to be used in vending and affixing machines These are valued significantly less than the imperforate stamp and care must be taken that the imperforate stamp has not had the Schermack perforations trimmed away. This is especially true for the rare type VII imperforate stamp where the used Schermack is worth much less than the used imperforate type VII.