Glad Rhett will chime in with additional info. I like information-laden long winded replies from authors!
On a side note I looked up John Rawlings on eBay to see if I could see if he was shown in any current sale offers as 2nd B. or 2.B. and came up with this unusual auction...
http://www.ebay.com/itm/1921-E121-Am...item22fb7f0dc6
BMW is claiming that this is "the only known blank-backed E121 to be assigned a numerical grade by a legitimate TPG". Seems to me that this would be a common W575-1 due to the fact that any blank backed E121 would be a W card or a Koesters. I am not sure what SGC was thinking calling it a blank backed E121. Derek, maybe that is partly to explain why SGC doesnt know what your Youngs card is either.