The most important thing in my collection would have to be this group of autographed index cards my father collected while selling hot dogs at Griffith Stadium when he was a teen.
He gave them to me when I was a young teen in the 80's and I unfortunately cut some of the better names to fit in holders. What can I say, I was a dumb kid. He also gave me a Senators team signed ball witch I promptly played with.
To this day I haven't been able to identify all the signatures. To me the highlights of the collection is the very early Mantle and the Hank Greenberg.