I recently had a lady that owns a fabric shop tell me that "charm packs"
were orginally what was (and still are) sent to the store owner to show the new line of fabric a company had and what they ordered from. She showed me a pack she had just recieved and there was a card on the back
that had numbers and that was what you ordered by. The numbers were in the order that the fabric was stacked, so she told me if I took one piece out to be sure I put it back in the same place so the fabric and the numbers would match up.
The were pinked on the edge so they would not fray.