How to tell if flywheel is iron or steel

Yeah dont worry, I wasnt going to grind on my flywheel.
Here are a couple pics of the flywheel. Its fully machined so no obvious rough areas like a cast part would have. Additionally, the numbers are stamped in.
Heavy? Hell yeah. I was thinking about 35 lbs. Threw it on my scale and its a whopping 40.2 lbs.

Flywheel_Front_A.jpg

Flywheel_Front_B.jpg

Flywheel_Back.jpg