The first Levi’s denim jacket style later known as the Type I jacket was the 506XX.
The 506XX was an early Levi’s denim jacket design associated with the company’s first generation of trucker-style jackets. It had a boxy workwear shape, a single chest pocket, and a back cinch that allowed the wearer to adjust the fit.
Collectors and denim historians use “Type I” to distinguish this early design from later models. The Type II, commonly associated with the 507XX, added a second chest pocket and changed the back construction. The Type III, associated with the 557XX and related models, introduced the familiar pointed front seams of the classic trucker jacket.
The model number is more precise than simply calling the garment a “Levi’s jacket,” because the company has produced many denim outerwear styles over time.