My hunch is that there are few references to it because it is rare. I found a reference to it being listed in Alan Herbert's book Price Guide to MINT ERRORS where it's reported to be a Hub Break.
Also in Hubbard's book on errors says that the '36 penny to "chalk them up to wear and tear" and "not all that valuable". It's a hub break as said before, but the noteworthy '36 is that they rehubbed the die with a normal R in Liberty and you got a nice example of hub-doubling.