Hi
Copper alloys that contain iron, nickel, manganese or cobalt may be attracted to a magnet.
Could be Nickel Aluminium Bronze as suggested by Andrew or maybe a Copper Nickel alloy which often have some iron content.
Both should be OK to machine the Nickel Aluminium Bronze being the harder and tougher material
Nigel
Edited By tractionengine42 on 27/01/2012 11:45:02