I believe these 2 ebay sellers are selling stamped/pre printed autographs as authentic.  They appear to be pre-printed as they look identical and in identical locations.  However, there are postcards (this is a 1960 era JD McCarthy Postcard) that exist that don't have the autograph on it.  see below.  However, you can see the company logos vary between the original and signed ones, so maybe they printed some with pre-printed autographs....any one have more info?

First a blank postcard.

Next an "autographed" one being sold by prfgrama with the description "This postcard was personally signed by Sandy Koufax at the Dodgers vs Giants game in LA in 1967.  My brother in law went to the game and was able to meet Sandy and get his autograph."

http://www.ebay.com/itm/131562380619?_trksid=p2055119.m1438.l2649&a...

Next another "autographed" one being sold by driprock, with the description: The autograph was obtained years ago in response to a request by mail.  It looks identical to the one above.

http://www.ebay.com/itm/391209885267?_trksid=p2055119.m1438.l2649&a...