Here's the skinny, straight from the USPS:
"2007 Holiday Knits
In 2007, the U.S. Postal Service will warm up for the holidays by issuing Holiday Knits, four stamps featuring classic winter-time imagery designed and machine knitted by nationally known illustrator Nancy Stahl. These beautiful stamps consist of a dignified stag, a snow-dappled evergreen tree, a perky snowman sporting a top hat, and a whimsical teddy bear.
In recent years, knitting has become quite popular again, both in the
Inspired by traditional Norwegian sweaters and knitted Christmas stockings, Stahl decided on "something cozy" for this year's holiday stamp issuance. She used a computer software program to draw her original designs and convert them to stitches and rows. Then she downloaded the information to an electronic knitting machine and used it to knit her creations. The machine's smaller stitch gauge didn't provide quite the effect Stahl was hoping to achieve. So she transferred the designs onto punch cards and used a different knitting machine that works something like an old Jacquard loom and has a larger stitch gauge. Stahl scanned the finished pieces into her computer and retouched the photographic images to ensure that all the stitches aligned properly. The result is a set of four colorful and "cozy" stamps that will add an extra touch of warmth to seasonal correspondence."