Back in 1966, the Red Sox traded once all-star reliever Dick Radatz for McMahon. As it would turn out, Radatz was washed up and was out of baseball a couple years later. McMahon was good in 1966 for the Red Sox, but wasn't stellar for them in 1967, essentially being replacement level. However, after being traded to the White Sox, he pitched very well and still had several seasons left in him.
So, this was a pretty good trade for the Red Sox and it's a good card for vintage Red Sox baseball card collectors. Excellent condition copies can be found for $2 or less.