Hi Fred! These were available in gumball vending machines in 1972. The latest guide I have lists Joe Greene at $4. The guide also mentions something about possible reprints, but I would doubt that someone did that - seems a cloth printing for cards that aren't in high demand doesn't make sense to me. I wouldn't be surprised if someone came across a large stock of these at one point, though.
Here is a listing for the machine header card. Neat set!
http://www.ebay.com/itm/1972-NFLPA-C...item2ea918c9a4
Happy collecting!