A fascinating and detailed study of the development and printing of the stamp process can be found at this site: http://www.dieproofs.it
For collectors of chess on stamps, a wonderful site with beautiful illustrations of chess stamps:
Other Useful Links:
THE FRENCH STAMP DIRECTORY - WWW.PHILATELIE.FR
Dealers, Auctions, Accessories, Magazines, Exhibitions, Clubs and more.
More philatelic sites of interests for topical and thematic collectors:
Currency converter: Convert instantaneously estimate or catalogue value in the currency of your choice. OANDA currency converter is amazing. It not only converts any amount from a choice of 164 currencies, but you can choose any date of conversion since 1990. We for example learn that One US $ was worth 138.31 yen on July 27, 1991 and 141.64 Yen on July 23, 1998. You can even all the rates for the last 30 days or over a period of your choice: