ID these wheels - Halibrand?

I need some help ID'ing these wheels. They are 16 X 4 with a 5 on 5 1/2 bolt pattern. Someone has attempted to polish the front, but the back is somewhat darkened. There is no name, only a cast "M" followed by three digits. The numbers are different on the two wheels. How do you tell if they are magnesium? Could they be early halibrands? They came with the '31 A I picked up yesterday. Pics:

 

Yes, they are Halibrands. And now for the obligitory "wanna sell them?"

 

Sent you a PM.