Thanks for the great comments! No it was not listed as an RPM, but you didn't have to look at the photo of the coin very hard to see this one. Some cherrypicks are made with a hope and a guess based on bad photos or just hard to see varieties. This one could not be missed either the quality of the coin or the RPM.
As for an S/S/S, yes, probably. The S mint marks from the 1940's are just full of minor split serifs and extra mint marks. This one seems to have a bit of a split upper serif and an extra lower curve line suggesting maybe a north as well. But it's so minor that likely even if an attributor saw it they would ignore it. Also, note that the coin has some mild
Machine Doubling to the north as well so careful which what you are seeing there as the line that looks like a lower curve on a third mint mark could just be the edge of the slide doubling. Either way, I wouldn't push it for an S/S/S listing.