Exhibits backs

[JTysver]

I am not too familiar with Exhbit Cards, but I have a couple that I'm not sure exactly if they are official Exhibit cards.
Please help me if you know something about these.

Most exhibits that I have seen slabbed or know they are reliable have a greyish dull back. In the mid 90s I picked up 8 "exhibits", 2 Williams, 2 Musials, 2 DiMaggios and 2 Mantles, each has a dupe.
The Williams and DiMaggio are in the 1939-1946 pose and The DiMaggio appears to be a reddish sepia tone, The Mantle and Musial are in the 1947-1966 pose.

Having a printing background, I examined these under a loupe. The dot pattern is clean and these don't appear to be built from a scan as it was really before the age of being capable of recreating on a computer. They don't appear to be reproductions and the pics match up to either the 39-46 or 47-66 exhibits.
The concern I have is that these seem to have lighter (and even whitish) backs and the backs seem to be semi-glossy or they have a sheen which doesn't match the more frequently found grey backs. which are dull.

I started to believe these were from the 1980 set but then I saw the cards in that set and these are not the same poses.

Can anyone tell me something about these?