Tim
I'm afraid it's fake - but it seems as though you expected that?
The main signs are on the shield and the jocktag.
(click on my thumbnails to enlarge)
JocktagCompare it to this one from my Cushing Texans' authentic. Note the differences int he red and white player outline (this is always the easiest to tell). Mine has a slight curve on the upper leg - yours is flat, which is always a dead giveaway. You can see other differences in the player and the ball in the shield (i.e. the seam on the ball in yours isn't quite right), which just don't add up. Also note the stitching on the outline of yours is quite erratic.
ShieldNotice the ball in my shield logo has the seam at an angle. It's also generally just cleaner, with no spaces between the red threads when compared to yours. Finally, and this is a really subtle difference, yours has white thread, whereas the shield logo is attached with clear thread for jerseys of that era.
Given the haul of Bills jerseys you have - if this is the only fake you have, you still have an amazing collection.
There is a helpful comparison of Reebok jocktags at the following thread, which is always useful for detailed comparison:
https://nfljerseyfanparadise.forumotion.com/t179-reebok-authentic-jersey-hem-tag-timeline