Adding the multiple items to your shopping cart versus hitting BIN you will be able to enter the code to make sure it will work before committing to buy.
Doing this has worked for me on previous offers.
As far as I know it was just a code in the link. It was not in my messages. If you want to try to see if it will work add the item to your cart and enter the code instead of hitting the BIN.
Howie Fox on a 1954 Topps is the rarest, he was stabbed to death in 1955. I have seen 1 and know where another is but the owner wants $2500. Others are Lou Jackson, Vern Stephens, Ed Waitkus, Dick Brown. Who I have about half of their cards. Still when you are looking for Multiple Bob Niemans...
I have spend the last couple years working on a 1952 Topps signed set and currently most of my funds have gone towards working on Orioles signed team sets from 1954-1970
Very much a thing but newish. Steve Grad left PSA to start Beckett authentication. Beckett and JSA no longer partner in autograph authentication.
http://www.beckett.com/news/beckett-authentication-services-launch/