That's a little different to the Sahara plaque example you gave.
The posters are not the originals. They are already the 'digital reproduction' or equivalent. Whoever had the posters made had rights to make them. No-one can inherit those rights without express permission. Had you taken a photo of the original (with permission/rights to use it) then you would have been ok. In fact you wouldn't even need the rights unless it was for commercial use, only the permission.

I had a cease and desist years ago for using some Playboy images when marketing the Palms Grand Opening chips. Despite the fact they were the same images the Palms were using, they didn't own any rights to let anyone else use them.

In the overall discussion here we are talking about photos or scans taken by the person that owned the physical plaques/jetons in the first place. In those cases only the person that took those pics can own the copyright.