Here are some tips on how to tell Gun
Metal from other metals:
Gun metal is a heavy non magnetic metal and looks very
similar to brass, gun metal is sometimes mistaken for
brass even by some of the most experienced scrap metal
The best way to tell gun metal from brass is to file it till the
colour shines through then compare the colour to the colour
on a separate piece of brass, gun metal has a very slight
pink tint compared to the golden colour of the brass.
Usually large industrial plumbing fittings will be made from
gun metal as it is a very strong metal and can hold the
strong water pressures.
It's always worth separating your gun metal from your brass
as it has a higher value, however most scrap metal dealers
will only buy as gun metal if it has all brass attachments
removed otherwise it will be just bought as brass.