I seriously doubt that a stovebolt crank got much, if any surface hardening, even when brand new and standard diameter. Getting a surface hardening job to penetrate more than a few thousandths would be quite a chore. Even the race cranks we paid big bucks to get nitrided only got hardened about .005" deep or so.
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!