My guess is that a Dick Tracy autograph would enhance the value of the books, since they are both known as great detectives. Now I don’t think that the value would go up as much as a genuine Holmes signature since it’s a Holmes book. I think that a Holmes signature on a piece or Tracy merchandise would have the same result, if not right away, than probably after the detectives pass on.
As a fairly new Dick Tracy fan, I really appreciate the great information Boboscar.