Hi Jon,

You know one thing, maybe I should call it a "striking surface distortion," because it isn't like the true "mushrooming," like you get on the top of a chisel.

I should also note that we use metal hammers almost exclusively for striking chisels and pegs, as that seem to be the norm in most places I have witnessed, or really hard wood mallets. It would seem about a 60/40 or 70/30 percentage, in favor of metal strikers over wood/leather. I personally have used an antique 750 g (26.5 oz) Japanese Diaku's Hammer (don't know the exact age,) and a 100 plus year old Trow and Holden 1.4 k (3 lb) Carvers Hammer for most of my life in furniture and timber wrighting. We use sledges with pads, when striking a frame or furniture or massive dead-blows. There is a few wood mallets and leather mallets around but they are light in weight and reserved for guests/students that don't have the skill or stamina to swing large traditional metal hammers.

Regards, jay