Many years ago i bought a 1908 (est) Foos 2 HP Tank Cooled stationary engine with a brass spark plug. I sold the engine last month, but kept the spark plug because it was unique, over 4" in total length, 3/4" pipe thread, mica insulation, take apart, with an extendable electrode.
Why a brass spark plug???? corrosive enviroment? near saltwater?? Opinions?
Anyway, here's a pic.