@SD, yes I definitely see what you are talking about and agree that it looks a whole lot like a letter S. However, as you may know RPMs are almost always much more subtle than that--with much less separation between the letters. Furthermore, I don't see anything so dramatic listed on varietyvista:http://www.varietyvista.com/02a%20L...%201928S.htm
Other than DDD and the randomness of circulation wear, I don't have a better explanation.
Added: I just noticed that you are a "big supporter" of CCF and wanted to specifically thank you for that. Well done for someone who doesn't have a whole ton of posts here.
"If you climb a good tree, you get a push."
"The danger we all now face is distinguishing between what is authentic and what is performed."