For reference sake, here is a similar piece that sold on eBay, framed in the same manner.
http://www.ebay.com/itm/1952-Topps-M...p2047675.l2557
Interestingly enough the Mantle sig is not good on it in my opinion. The color of the Mantle card and creasing is very similar to the OP's. Unless the camera flash is doing something odd, the creasing does not appear right on either, it's just too white at the breaks especially on the reverse.