This is a Minnesota Vikings game, football jersey from Sand-Knit. Based on its design it's from either the 1970's or early 1980's. The collar has been removed. It was purchased from the NFL auctions website in the early 2000s.

It has an NFL, PSA/DNA sticker on the back of the neck to verify its authenticity. Unfortunately, the information on the PSA website is incorrect as it id's the jersey as having been signed by #46 and worn in a game on 11-10-2003 both are wrong. It hasn't been signed and the jerseys in 2003 were made by Reebok and also look different with the Vikings' logo on the sleeves. 

The jersey is a size 42, and when measured while lying flat it is about 22" from armpit to armpit and has extra length measuring about 39" from the back of the neck to bottom hem.