Well, after emailing him about it, Tod acutely pointed out that the Greason blob has 2 makers' marks! The D.O.C. on the heel stands for Dominic O. Cunningham, out of Pittsburgh, which I already knew. But I didn't know that the "WB" monogram on the base was used by the Wittemann Brothers of Buffalo NY! After noting this, I looked on Tod's site, and saw that THIS BOTTLE, which is from Jersey too, not only has the peculiar "MUST BE RETURNED" embossing, but it has the "WB 57" mark on the base! This pretty conclusively, at least for me, shows that for whatever reason, this bottle has two makers' marks. Your guess as to why is as good as mine.
My guess is that one company sold one of its molds to the other company. Most likely the Wittemann mold went to Cunningham, as the majority of the embossing indicates manufacture at Wittemann. Maybe, Cunningham added his own heel mark to signify the bottle having been made there, but he didn't scratch out the other embossing of the bottle. Very peculiar, at any rate. We'll see what Tod thinks when he gets back to me... [:-]