Nickel plated brass.
6 Pin.
GA Section.
Various key blank manufacturers may call this key by a different part number.
Some examples are:
Cole Y78 Curtis
Y-78 Dominion 8GA
Ilco 998GA
Ilco EZ Y78
Jet 11GA
JMA YA-57D
Original EN11GA
Orion YAL15A
Silca GYA6
Star 6YA12
Taylor 12GA