@benderz00 I think the Mantle is 1-1.5 max due mainly to the severity of the crease. Spahn might be in the 4-4.5 range. The idea I try to follow is that cards grade "down" to their weakness, and then "up" from there usually no more than .5-1 point. I know they don't assign actual "subgrades" but the idea is the same: if a card surface is deemed "3.5" AND that is the weakest feature then 4-4.5 is the likely grade. But yeah, the question is: just how hard do they hit the stains? Given that there are 2 of them, I think they would grade the surface low. Thanks for submitting--report back if you grade these. 

This '77 Nolan might help with the impact of stains on the back (though this is PSA rather than SGC). I picked this up for $20 and absolutely love it. The front looks 7.5 or better with pretty much perfect centering. But the big gum stain on the back brought it down to a 4. So I think it brought it down 3 or more grades. But I actually like the stain: It makes me think of a kid pulling this otherwise gorgeous card out of a wax pack back in '77.

Michael, Thanks for that example and information. Did a quick Google search, 6 cards in a wax pack for 1952 Bowman... so about 1 in every 6 cards from 1952 Bowman could have a wax mark. Another Google, 10 cards in a wax pack for 1977 Topps. 

Follow-up on the 1952 Bowman Spahn, which I submitted to SGC in November... Came back with Evidence of Trimming tag.... One reason I got the Spahn was to get a 1952 Bowman for my run of Bowman cards, so no other 52 to compare to... I am sure they have a bit better tech than my tape measure... How do others measure their cards?

Sorry I missed this follow up! I'm lazy and generally measure them against other cards! Some use digital calipers. NOTE: a card can be trimmed and still measure! A couple of examples: 1) A card that was factory "large" is trimmed down to size to improve centering; 2) some fraying around corners is trimmed away without changing the nominal size of the card. Hope this helps!