Teresa, that suit is gorgeous! Honestly, Jonathan Logan stuff from the 50s can be awesome--so many people haven't had the pleasure of seeing the early things and just "assume" they are like the later 60s & 70s stuff (the early/mid 60s stuff was great, too--with their trendy mod junior looks).
I wouldn't say that is technically a portrait collar, but reminiscent of the look--it's the first collar term that popped into my head when I saw it, though it would be set wider out on the shoulders and might be cut a bit deeper if it were a true portrait collar. Perhaps a "modified" portrait collar, or a portrait-inspired style? Not sure there is a technical term for it. Whatever one calls it, it's lovely, and I should think very flattering.