A synoptic key to the catalogued envelope stamps of the United States
Subtitle: being a system of alternates such as is used in botany and zoölogy in the determination of plants and animals, a system unique in philately and so simple that a child can with accuracy determine the most difficult die of the United States envelopes.
By: Illustrated by a plate of 70 figures and a color strip of real envelope paper representing all colors used in their manufacture, by A.N. Caudell ...
Publisher: Printed by Judd & Detweiler, inc.
Published: 1914
Place of publication: [Washington
Language: eng
Number of pages: 14
Subjects: Postage-stamps -- United States.