"George St. George" was not a pen name of St. George Rathborne, although it has been so listed. Rathborne(1) himself acknowledged "Harry St. George," but in a list submitted to him crossed off "George St. George" as a name under which he did not write.
Dime Library. Nos. 296, 417
|1||In litteris, St. George Rathborne to George French, July, 1934.|