The signs for the fake Mantles are mostly in the wear on the cards -- if you look at the back of the Bowman, you see "crazing" lines with some tone coming through. I've ONLY seen that kind of wear on artificially aged fakes -- you see some of the same kind of wear on the front of the Cobb. The edge wear is terrible, too -- hard to articulate, but it's not what you see on vintage 1950s card stock. At the bottom, you can see how the white-ish color of the back is wearing off, which it should not -- that color should be part of the cardboard itself.
compare to (a random image find) this real card with some wear:
https://cdn.shopify.com/s/files/1/12...g?v=1528823538
on the 1960 there are fewer red flags but the image quality is terrible -- see Mantle's head/hat, the blacks are all running into a big mess, vs. the clear, subtly toned original.
Also they both appear to be hand cut on at least one edge?