[canjond]

I think the popularity of the player, whether the signature is "playing day" or not, and the variation in signature matter most.

With someone like Berra, there would be some difference in value between a "playing day" signature as opposed to a later in life signature. I'm not sure the difference in values would be extreme, however. Stylistically, Berra's signature didn't really evolve over time.

Someone like Mantle, however, the difference could be huge. A 1951 signature of Mantle will be worth many multiples of what a "later in life" signature of Mantle on the same medium would be worth. Not only is the "playing day" signature more valuable, but his style of signature evolved over time, so there are very few early style examples available.

Also, with people like Cy Young or Honus Wagner for example, their signatures became very "drawn" and shaky later in life. A nice, crisp earlier signature will be worth more than the "later in life" variations.