Hi All. Me again!

I have been watching a lot of online tutorials about how to use and what to do with a chasing/repousse hammer and I quite fancy getting myself one. However, I have what might seem a rather stupid question....

All of the tutorials I have watched show and mentions that that face of the hammer is slightly 'convex' which help eliminate 'edge' marks on your work. However, when looking at ones to buy - they all seem to be flat faced. From what I understand flat faced hammers leave marks if not used correctly. Am I missing something?