I thought I was mis-remembering so I did a little googling and it seems that he used a Louisville Slugger in the early part of his career and later in his career he switched to an Adirondack model. I don't imagine that was a very common thing to do. What you have is probably from the 60s (my Adirondack model was in the 70s). I'd hang on to it, it's a pretty cool item.