On all the Piedmont's, the stamp runs at an angle similar to the frame of the back. They go from running off one side to running off the other, and I have found two that are different than all the others. Those two run top to bottom (or opposite of what you would see a library book spine on a shelf). All the others read top to bottom, but upside down. (the example of the two oddballs are in the SGC article). All the Hindu's and Old Mill's run like a book spine, top to bottom, but centered in the card.
Overall condition of the cards would probably grade fair, but you don't know how much of that is because of McCormick's treatment of the cards, or the treatment since they left his hands. I've got a Hindu backed Sullivan that looks like it was a rat treat, and is missing almost every corner entirely, while I have seen (but don't own, and probably never will) a green back Cobb, that if not for the stamp would probably grade an 6 or 7 (it was graded by GAI and got a 2, but it is a very, very nice 2).
I've not seen any with a wet transfer. And the look of the stamps being all over from side to side, but following the same pattern leads me to believe this wasn't a "I'll sit down tonight and stamp all my cards" type project. I've posted this link before, but it will give you an idea of what the first 30 looked like in terms of condition and where the stamps were
http://s150.photobucket.com/albums/s...t=7a2e9b2a.pbw