I have a couple of photographs with a halo of sort on the face of the subject. It isn’t a stain but was taken like it. Maybe a defect on the actual photo paper? I’m not familiar with the kind of camera used for RPPCs. The black edge on the left is original of the photograph too and not from my scan.
Anyway, the gentleman on the right is sporting a long mustache, a boat captain hat (?) and a butterfly wing collar with a few rings. His friend (or brother?) is wearing an overcoat and short rimmed square top bowler.
This RPPC came from Estonia.