Zombie or Sig wanna take this one?
Sure. First, here are the basics:
1. The Dude's sweater was made by Pendleton; it debuted in 1974 and was called the "Westerley". The style is "cardigan" and the pattern is commonly referred to as "Cowichan" (though there are countless Cowichan patterns). Note: Due to the sweater's popularity, in 2011 Pendleton released a "tribute" sweater they called the "Dude". It's also a cardigan with a zipper, but the colors and patterns are different from the Dude's sweater.
2. Unlike most cardigans, the Dude's sweater has a zipper rather than buttons. The zipper itself can be a point of contention among die-hards, since zippers on older wardrobe items have often been replaced. The zipper on the original sweater has a 1.5" diameter "ring pull" tab, and was made by YKK.
3. Colors. The Dude's sweater is primarily light tan/cream. The horizontal stripes are dark brown, and the Cowichan pattern is black. This is important because Pendleton made the sweater with the same patterns in at least eight different color combinations.
Now, there are some "imitation" sweaters available. "Homemade" and "custom" sweaters are usually fairly accurate, but the mass-produced sweaters usually differ in some way. Here's an example:
A. On the original sweater, the "Z" pattern is the same on the left and right sides of the front of the sweater. On the replica, the "Z" pattern is mirrored.
B. The position of the "center" pattern is slightly different on the replica.
Hope this helps!