Previous employment required using brass, bronze, or copper only.
No steel hammers allowed as we maintained molding machines and the company
was leary of using steel close to the molds themselves.
To include no steel pins / wedges allowed in alloy hammers to attach / secure the hammer head either.
One benifit of no steel hammers is its harder to damage the ends of a shaft when trying to coax a shaft out of a machine or bearing.
Not saying it can't be done, it just takes more effort to damage a shaft with a soft hammer.
As far as types, I've used copper brass and bronze, can't say their is a whole lot of noticeable difference between the three other than copper will mushroom quicker / easier.
Never used a lead hammer at work.
Of all the alloy hammers I've used Lixie makes some of the best and that's what I purchase for my technicians.
I get them from Travers Tool
Lixie website
http://www.lixiehammers.com/