Another Diamond Giveaway Trade

A few days ago, I traded a 1974 Topps Jim Merritt for a 1975 Topps Rick Dempsey. After that, I started to get a few offers for the Dempsey. Is there something special about this card that I didn't know about? I checked eBay and there are plenty listed for around $2, so I don't really think so. Anyone know?

Anyhow, someone offered me a 1976 Dempsey (Yanks), a 1977 Fran Healy (Yanks), and a 1978 Stan Bahnsen (Expos) for my '75 Dempsey. Two Yanks and three cards overall from the '70s? Done deal. I only had four cards up to this point, and wouldn't mind grabbing some more trade bait, so I figured it was a smart deal on my end. I'm not up to six cards from the four codes I redeemed.

I got:

 

For my: