The date is WAY too large to be real, as there are no date varieties known for 1870, and the serifs are wrong as well. I'd give you $1 for it to put it in my 'Oddities' bin and sell for $2 at most.
Regardless of law I would never resell it if I had it as I wouldn't want it back into the population to dupe some other unsuspecting collector and possibly turn them away from the hobby.
I agree - in fact, to me it looks like a small motto instead of a large. I'm pretty sure that the large motto was the one used from mid 1864 on, and then the 8 - that 8's bad serif is worth 1,000 words on its own.