It looks like it may be an actual missing color. Red is tricky because it fades so much from light.
The couple T206s I have that I believe are actually missing color are missing at least two colors.
So if it's missing one of the other colors I'd say it's most likely unaltered.
Value is always difficult with these.
I'd have bought it for sure at $21, and probably a bit higher. Hard to tell where that limit would be, 40-50 might make me pause a bit. Others would stop earlier or later.
At the $640 of the Ebay BIN I'd probably be out because of budget, but with a really good scan I'd be interested.
I think Robs suggestion of auctioning it on Ebay (Or even here) would be the best route. The question then would be the starting price.
I've picked up a few nice cards on Ebay I think because others avoided an auction for what looked like an altered card.
Somewhere well above the $21, but also well under the 640 ........Yeah, I'm not being real helpful on price.
Start with a nice big scan, 600dpi, maybe Higher. 1200 will show nearly everything.
Of course that would have to be hosted somewhere besides here or Ebay where the scans get reduced.
Steve B