a marked ruler used to measure the number of perforations per unit length along the borders of a stamp.
Origin of perforation gauge
First recorded in 1890–95
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British Dictionary definitions for perforation gauge
a graduated scale for measuring perforations and roulettes of postage stamps
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012