I probably should have clarified further. The image I posted is from a real, completed helmet. Around TDH, it's been labled the Preproduction 2 helmet; it was the helmet featured in all the early pre-ESB promotional material, i.e. the Fett action figure cardback.
The only reason it's referred to as a Preproduction helmet is because it ultimately wasn't used on screen. Except for that caveat, its features, including the dent, are virtually identical to every other real helmet, including the ESB and Jedi helmet.
The dent on the Preproduction 2 photo, the dent on the helmet in the archives book, the dent on the Jedi helmet (except for a dremmel mark) are the same.
So, the differences you see in the comparison picture between the BM dent and the Preproduction 2 helmet would be the same regardless of which film helmet you compared it to.