Contest winnings from Johnny's Trading Spot

I got two 1977 Pepsi Discs in a contest win from Johnny's Trading Spot. Mike Hargrove and Butch Wynegar. I have a couple of other discs already but these are my first that are still attached to the packaging.

 On the back, you can send away for a shirt that says "To my Buddy, "Chris", Best Wishes, Pete Rose." Or Joe Morgan, Rico Carty or Rick Manning. I wonder how much a shirt would be worth today. I couldn't find any online, but here is a picture of a one, along with a Carty shirt, from a Pepsi wall display, from 4192cards.com.

 You could these shirts for "free" if you drank 240 bottles of Pepsi.