That look like a well preserved chrome print? Was it 11 x14? Wonder if thin stock or triple weight. My guess is thin and mounted - signed on the mount.
I see - it was a 10.3 x 13 offset print of that original color print/transparency. This is like a magazine image. Not on photo paper at all I think. Having read the auction description I would like to think they would have mentioned if it was on some sort of decent stock of the day to maximize desirability. Without that I must think magazine-like stock and it does say signed on the mount, not the mat. On the other hand other examples appear matted but have some text or credit lower left under the image.