Howard,
If you do a search on Legendary's website (click the history tab), they sold a Clemente pin like the one that you have. They have it dated 1960s although I believe it to be early 1970s. I have also seen that pin sell 1-2 times on e-bay in the last 5 years or so, for much less than Legendary sold it for. I have a poster with the same image which I attributed the date from the 1970s...
A good person to talk to would be Paul Muchinsky, he may know more info, but I don't have his contact information....sorry. I have e-mailed him in the past about pinbacks and he was always very helpful and informative.
I was a long time Clemente collector, but have slowed collecting his items as I have focused mainly on pre-war for the past few years. I would enjoy seeing some of your more "difficult" Clemente items if you care to post them. I have always regretted not picking up the Sugardale and punch-out, but hey you can't have it all. However, I did acquire a couple of my "holy grail" items of his, including his nodder, the WADO pin, and some sigs. Looking forward to seeing some of your collection.
Mike