freight cars wheels

Quick question about wheels on freight cars… While train watching, I notice that on some freight cars passing by their was a white H on some of the wheels. Any ideas on what the H is for?

Thanks for any ideas.

Sorry… I guess nobody knows.

I’m pretty sure it is to signify if the wheel has had a certain heat-treating process. A carman would know more, and probably paints the “H” on there.

The H stencil painted in white indicates the wheel is a heat-treated curved plate wheel. Matt

Thanks, for the help.

Spjoey