One note, as per Hopcar's check with his supplier and the strict no-lead requirements in plumbing
valves and fittings in current
building codes, I think you will find that a lot of the 85,5,5,5 bronze will be using aluminum
instead of lead now a days. Not so much in seacocks but in the NPT fittings and valves.
The difference is now you have 10% sacrificial metal in the casting (5% zinc and 5% aluminum) where before only the zinc had a high galvanic voltage potential. But its only 10 percent of the metal so not a major problem structural wise.
Yes there is not a true standard in when you have brass and bronze as many ASTM numbers tend to flip flop weather
its bronze or brass. Something about too many cooks I think.
But the general consensus is anything 77% to 87% copper is bronze and anything less then 77% is brass. So despite with the code committees call it, 85,5,5,5 is bronze. Though to me anything below 80% is brass. But I'm picky.
Of course then you get into the whole issue of something stamped with an ASTM number not actually meeting that standard. That is a problem with some pipe, fittings from a large asia
country. Seen it first hand.