[UnbelievingScumOnTheOtherSide]

But that said... it’s the southern coast (the Argentine coast) that really doesn’t match.

But it does. The Argentine Valdes Peninsula and Puerto Madryn under it are an obvious feature along the bottom. Valdes Pen. Further to the right along the bottom, the coast follows the curvature around the Gulf of San Jorge to the point of land at Puerto Deseado in the bottom right corner. That is more than enough, given the quality of early cartography, to be conclusive.

[Ramius]

Yes, but there are other prominent features that are skipped and don’t have a counterpart in the other map.

I’m not saying that I think it is antarctica, but the northern part matches better, feature for feature, than the southern part.