In 1915 the complaint that the "perforated ten" stamps were difficult to separate caused an experimental issue of two cents stamps with a new type 11 gauge perforation. This having proven satisfactory was soon thereafter used for all flat plate stamps. The use of ten gauge perforation on the rotary press printing, however, was necessary because the method used needed sufficient uncut space to prevent the sheets from tearing apart in the perforating process.

The introduction of rotary press sheet stamps for general use again caused this complaint and it necessitated the development of the bar and wheel type of perforator which made it possible to decrease the amount of uncut space between the stamps and increase the ease with which they could be separated.

In December 1926 the two cent stamps were issued with this new form of perforation as an experiment. Having proved successful other values were issued from the new perforators as soon as the supply at the Bureau became exhausted This value was not in great demand at this time and not issued in the new type of perforation until June 10, 1927.

A first day cover of #638, dated July 27th 1927

A sheet of 100 of #638