I would have to do the old machinist's "spark test" on the gear to make an educated guess about its composition. Gently touch the part to a bench grinder wheel in a location that won't compromise it, and look at the color and shape of the sparks the wheel throws. Bright colored feathery-looking sparks are high carbon steel, while orange sparks without little or no "feather" indicate soft steel or cast iron/steel. The problems arise when a steel gear (early 235 or 216) is run against a cast iron cam. The hard gear machines away the cam metal. A cast iron gear can be run against a cast or a steel cam without any problem. It's also possible to run a bronze gear (a 230/250 six racing part) against a steel cam. Bronze wears quickly when driving a very high volume racing oil pump, but it lasts about 3 days past forever on a street machine with normal oil pressure.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!