1. the cutting edge of the machine which cuts the envelope blank.
2. the size and shape of the die-cut papers from which the envelopes are folded.

Perforation	Perforación	Perforierung	Perfuraão
Perforering	Perforering	Perforazione

Perforations are measured by counting the number of peaks or valleys in the perforating in any given 2cm space.

A 11 x 13 has 11 perforations in 2cm on the top (or bottom) and 13 on either side. A single number measure means that the perforation count is the same on all sides.

A 10 verticle means that both left and right are perforated 10 and the top and bottom are not perforated. 10 horizontal means that the top and bottom perforations are perfed 10 and the left and right are not perforated at all. These last 2 are usually coil stamps, issued in long stripes or coils, one stamp wide, so for seperating the stamps, only 2 sides need to be perforated.

Perforations are usually measured using a ^lsupplies/philatelic_tools/perforation_gauges,perforation gauge}. ^^24179

1. Refers to English Stamp Act of 1765-66 to be applied to newspapers, almanacs, advertisements, playing cards, etc. Embossed stamps were die sunk with a heraldic design.
2. British Parliament Act of 1765, repealed in 1766, imposing a duty on various types of paper used in the American colonies; have word "America" in the design. ^kTea Tax}

1. since most stamps are printed on paper, faults in the paper are sought by collectors as freaks or oddities, in some cases, the type of paper is important in the identification of some stamps.
2. first used as writing material by the Chinese, 2nd century
3. BC.papier (French, German, Dutch); carta (Italian); papel (Spanish)