The Tools You Will Use : Page 89

Because many stamps of identical design on identicalpaper have been manufactured with different gauges ofperforation and because such differences are often ofgreat importance in determining the value of a givenstamp, the perforation gauge is a very important instru-ment. However, it is unnecessary to know or to determinethe gauge of perforation of every stamp in your collec-tion. You will find use for the gauge only when identicalstamps are separated from each other — in your albumor in the catalogue — because of different perforations.This happens frequently with United States stamps in theearly twentieth-century issues when the Bureau of Print-ing and Engraving (where all United States adhesivepostage stamps are now printed) was experimenting withvarious methods of perforation. Most all current UnitedStates postage stamps are now produced by machinesthat provide the standard "Perf. 11 x 10 1/2." (The hori-zontal top side of the stamp is always given first, followedby the right side, and then, if necessary, the bottom, whenindicating compound perforations.)