European signs were often convex, especially before 1950s.
I have several original Swedish signs that are convex, including Mobioil, Shell Fotogen (Kerosene), SHELL bensinstation, Texaco Bensin och Motoroil, Essolube Motor Oil,
AGFA film, Persil...
In the old days the shape was often hand made with a hammer.
I am sure this is different for many markets