Many people confuse a Bellied Grind and the Double Concave
This is a good thread that has the old George Korn Patent on it too
https://sharprazorpalace.com/razors/...ied-grind.html
The bottom pic of the razor with it open shows the Double Concave lower edge quite well
The are a unique feel on the face
Victor aka Bluesman on here does a great version of it
Korrat also has a version