It had long been believed that these booklet stamps were issued in September, 1914, following the initial appearance of the perf. 10 sheet stamps. In 1933, copies of one and two cent stamps, perf. 10 on three sides were found. on covers dated in February, 1914. The stamps on these covers all having a straight edge on one side seemed to indicate that they came from a booklet pane. Under the belief that these early booklet panes may have been the result of an experiment at the Bureau, the matter wis taken up with Alvin W. Hall, Director of the Bureau of Engraving and Printing.

A booklet stamp can be identified positively if it has a watermark. The watermark will be vertical for booklet stamps and horizontal for flat plate sheet stamps.

Flat plate booklet stamps are not the same size as flat plate sheet stamps or any rotary printed stamps. A booklet stamp size would is wider than a flat plate sheet stamp AND narrower than a horizontal rotary printed stamp

As the curved plates of the Rotary press made the stamps slightly larger it is relatively easy to discern which stamp is flat plate and which is a rotary press stamp. First select any perf Washington Franklin stamp or the first issue Washington Franklin 1 cent or 2 cent. These are the stamps with the numbers one and two spelt out, instead of numbers being displayed. I chose the latter alternative as shown in the first image above.

Then cut out squares at each corner. As shown in the second image above. Placing the stamp you wish to test under your cut out stamp you can see if the frame lines match. If, as in the last image shown above the frame lines are outside the top stamp in either the top, bottom or sides then you have a rotary stamp. If the lines are in the same place, as shown in the third image, you have a flat plate stamp.

This test works with any value stamp.

The flat plate press

Bust of George Washington
by Jean-Antoine Houdon
1785
The source of the design