I think you're right! The OP's copy looks like a U10 with "medium wide top label with curved ends". The nystamps copy looks like a U2 with "short top label with curve ends". Notice the distance between the "THREE" and the curved border is a lot shorter on the nystamps copy (hence the short top label of U2) versus the wider gap on U10.
Offsets (or set-offs) are popular printing varieties for EFO collectors. Here is one of mine.

I agree with revcollector, that is a great socked-on-the-nose Kansas Territory cancel. According to Wikipedia, the Council Grove post office opened in 1855, and the population of the town was just 712 people in 1870. There can't be too many copies of that cancel floating around. I think the value of the piece is enhanced more by that particular postmark rather than the offset on the reverse, though the combination adds even more uniqueness to the piece.
Given the $4 catalog value of U10, if it were mine, I might list it on e-bay with a starting bid of $10 and see what happens. Though it is such an interesting piece, for that price I would probably hold on to it rather than sell it.