Card Identification Forum

Hi all,
I stumbled upon this set only recently on TCDb - and now I looked up the Forum, too.

Actually, I initially searched not because of the a.m. Holo cards, but because of the non-holo Babe Ruth ProtoType card which is also listed under this set. I have been very happy to find this listing of said card at all as I have tried to find it here  or elsewhere for quite some time.

Well, I actually have 5 different non-holo Prototype cards - 1 each for all 5 Players, i.e. Ruth plus Cobb, Gehrig, Wagner & Young.

All 5 cards have PROTOTYPE printed on their back, the other text on the back is the same for all cards, backs are b&w, fronts are colored head-shots. While the Ruth card has printed UPI/Bettmann alongside the picture on the back (as in the scan), all other four read Nat'l Baseball Library.

Unfortunately, I myself have no further information about these cards whatsoever.

I appreciate any additional information if anybody had any and also any advice on how to continue best with regards to the other four cards apparently not listed yet - Thanks a lot!