Levi's used Talon 42 zippers in late 60s & throughout 1970s. By 1980 they were using Levi's branded zippers. Levi's added the 505 to the Orange Tab line in the early 80s. Sometimes it took a factory a longer time to use up supplies such as zippers before they implemented new materials, and that's most likely why these jeans have a 70s version of zipper while they weren't actually manufactured until early 1980s.