Hi Tom, can you offer some more insight that may help us mere plebians? I don't see any obvious signs of funny-business regarding the toning. And, given the white balance is off in the images, and the luster is not well represented (it's a good photo, but not a great one), I'd love to know a more detailed response to the question of what sticks out to you about the color besides a one word black-box answer of "experience". I have seen lots of über-graded SLQs in problem-free slabs with much wilder and questionable color.
on the toning: the rev looks pretty natural to me. the obv is where I have problems. first, the color looks sort of layered on over top of the surface. Second, you just don't see that kind of color on 1917's in their natural state. third, it just covers the whole obverse which is unusual on a SLQ. I looked through a few pages of images on Heritage and just didn't see anything similar to this coin. Some coin series, even some years within a series, have tendencies to tone, or not, and usually tend towards certain colors and patterns. It is subjective, true, but one has to be skeptical of the outliers.