Look at it really close. I think that the decal has been cleared over. Also, it appears that a piece of tape might have been on the underside.
So,in essence, the NOS might just be a decent repaint. Come to think of it, the seller said he was selling it for a friend. The perfect excuse to deny knowledge that this is a repaint instead of NOS.
Most Honda tanks had a base coat and a color coat of candy that often faded with time. I bought a brown early 750 tank, and the color on the underside [the base color] was green. The decals on OEM were not painted over but the decal on this tank in the picture looks too shiny as if it was cleared over.
That high price had me fooled into thinking it was original at the time. Also,what are the odds the tank would be sitting on a cardboard box that had been used to pattern a spray gun??? Sure looks like base/clear to me.