I picked this up on EBay at a good price. It looks to be a legitimate one of one card of Herschel Walker. It's basically a one off of this card:
This is the "Emerald" example of the base card, which is serial numbered to 5.
The patch on the front is ripped, which probably explains the price. Admittedly, the eye appeal of the top card is not great, but I'll take it.