Hi Scott and welcome aboard , IMHO when it comes to signed cards the value is not combined , It becomes whichever is greater, the signature or the card. That is the reason signed cards are the favored medium of forgers , Where its possible to turn a $5.00 card into a $500.00 card, For example a 1952 Mantle in reasonably decent condition is favored unsigned instead of signed because the signature is far less value than the card. Perhaps because you are dealing with two different areas of collecting. The card collector and the signed card set collector. Using the same comparison take a card of a common 1950's or 1960's common player that may have had a tiny window to sign the card and the card becomes extremely valuable with the signature and of almost no value without it
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