Here's the box. $20 on Craigslist. Its obviously been repainted at least once. Its very heavy. I don't see any stamping on the back, but like I said, its been repainted with a pretty heavy coat.
What do you think? SO? About what year? My guess would be 60s.
Edit: I found the stamping. It is a snap on KRA59C, "Kenosha, Wisc USA 77"
I don't know if the 77 refers to the year or an old postal code.