[VoodooChild]

Hey Brian, nice find. I don't know much about the Neilson's but your example is similar to one of the E121-80 back types. The E121-80 Type 1 back can be found printed regular and in reverse. Rhett Yeakley, who's done the research on them, doesn't consider the reverse printed back as a new type, but rather a variation of the Type. There is a Type 4 back that is found printed only in reverse, but it has a "smaller" line of text and it's that different characteristic that I believe is the reason Rhett considers it a separate type from the Type 1 reverse back variation.

I can't tell from your scans, is there any other differences in the backs other than being printed in reverse? All that being said, it's a cool find and could be very rare whether it's defined as a new type or not. Congrats.