 For example, the Scott Catalog used value listings for the German Democratic Republic are for CTOs from 1950 through mid-1990, over 2700 stamps.Forgers have not only manufactured stamps for the philatelic market, they have added forged cancellations to those stamps.This was especially common in the late 19th century and early 20th century, when huge numbers of inexpensive stamps were forged for the packet trade.