Actually, there is an explanation. The style of those Sand-Knit tags were used in roughly 1981-84. The Raiders didn't move to L.A. until 1982. This could be a circa 1981 jersey shell that was prepared for Schroeder to use in the late 1980s. Although very unusual, I've seen as much as 10-year gaps between the year the jersey was made and the year it was worn in that era of NFL gamers.

Dave Miedema