Artist Trading Cards
They are the little cards that have become a big deal:
Artist Trading Cards (ATC) are collectables, a brilliant idea born of the sports-theme trading cards. They were first created in Zurich in 1997 by M Vanci Stirnemann and have been spreading quickly since.The whole essence of these tiny works of art is about artists exchanging their works and getting exposed to many personal styles.
Artist Trading Cards, better known as ATC’s,
are masterpieces in miniature that you create and trade with others.
There really is only one rule.-Size: 2 ½ x 3 ½” cardstock. This is also the size of most playing cards, Other conventions that are followed:
-ATC's must be traded, never sold.
-On the back of each card the artist puts their signature and writes
part of all of the following information:
Name, contact information, date, title of the ATC and number 

(1/7, 2/7)
By definition, ATCs are made in small numbers, often no more that one of a kind. Unique ATC's are called original, sets of identical ATC's are called editions and are numbered as above. Sets of ATC's that are based on one theme but that vary are called series and are numbered also. An original may be copied for a series or edition, however, there should be additions to the card after making a copy.