No data to back me up, but I would say on a low grade card (maybe PSA 2 and below???) it would increase the value.
STAY HEALTHY!
Doug
Liquidating my collection for the 3rd and final time. Time for others to enjoy what I have enjoyed over the last several decades. Money could be put to better use.
On Mantle's 52 Topps, I don't know what comparable unsigned cards would have sold for but here are some examples of ones that have sold that have been autographed. They are not particularly hard to find, there's usually one or two on ebay at most times. Here's a few sales for you to get some data from.
This one sold for $14,340 back in 2008 at Heritage Auction Galleries in Dallas
This one sold for $22,325 back in 2011 at Robert Edwards Auctions and was described as VG to Ex for the card condition
This one sold for $3700 at Bussineau Sports Auction in the final quarter of 2011, and it was flipped on ebay in December 2011 for $4500
Comments
Doug
Liquidating my collection for the 3rd and final time. Time for others to enjoy what I have enjoyed over the last several decades. Money could be put to better use.
This one sold for $14,340 back in 2008 at Heritage Auction Galleries in Dallas
This one sold for $22,325 back in 2011 at Robert Edwards Auctions and was described as VG to Ex for the card condition
This one sold for $3700 at Bussineau Sports Auction in the final quarter of 2011, and it was flipped on ebay in December 2011 for $4500