Small difference can affect stamp values

Gustamps are sometimes asked to explain the difference between stamps which seem the same. Quite often stamp collectors bring stamps to Gustamps and ask why when they buy a packet of all different stamps, duplicate stamps are contained in the packet. Gustamps explain that sometimes differences in stamps are not that obviously apparent. Gustamps point out that a common difference are watermarks which are not always easy to see. Gustamps add that perforation sizes can also make a stamp different. Gustamps also tell collectors to check out graphite or phosphor markings. Finally Gustamps point out that stamps often have small printers imprints on the base of the stamp. Gustamps say collectors should be aware of all of the different variations on stamps, as it can affect stamp values.