Put a magnet to it. So did some reading, im guessing clutch springs are this stuff cheep and just across the way from mobyland.
"Silicon Manganese: This alloy steel is quite popular in Great Britain. It is less expensive than chromium-vanadium steel and is available in round, square, and rectangular sections in both annealed and pre-tempered conditions in sizes ranging from 0.031 to 0.500 inch. It was formerly used for knee-action springs in automobiles. It is used in flat leaf springs for trucks and as a substitute for more expensive spring steels."
Not sure if mentioned in post but u can drill the spring n bell and add a third rivet.