Good spot Doug - thanks for posting!
In solving my issue, I realized the source. I based my ids on the photo below and without examining it terribly closely, did not realize that there are a few differences because people shuffled around between the two photos and the photo below has a two more people in it.
It turns out it makes mine one-of-one as the photo below is the only other 1947 Whiz Kids photo I can find. I'd like to think that Ben Craig, in the top row of the other photo and missing from mine, was late to the shoot so they had to take another photo after he ran up --- this would make mine the very first baseball photo of Mantle and the only copy.
I've updated my initial post accordingly. Thanks again for checking my math Doug!