Starting from the original US bomber jacket, we added a sheepskin collar and a lot of little pockets both on the front and on the back of the jacket. Those pockets were formally used as compass holder.
The Quartermaster Corps was called upon to develop special items of clothing warm enough to protect tank crews in severe winter weather. Key features desired were that the uniform should be close fitting with a minimum of protrusions, so that it could be worn in the close quarters of a tank interior, and so it would not catch on obstructions and slow a man getting out of a burning vehicle.
Based on these requirements, those items were designed for the Armored Forces early in 1941 and were manufactured and issued to units before the end of the same year.
The Tanker Jacket was worn from early in World War II until the uniform standardization of 1979. As with a few other items of military apparel, it continued to exist just beneath the official radar long after it lost its official Stock Number.