It's hard to tell for sure because there's so much crud and rust, but it seems too thick and clunky to have been cast as a griddle. Also the wide, flat edge didn't make sense to me as a griddle surface. It just seemed more like a stove part. But I guess some early griddles might just have had a short handle and a rough casting! I think the next step is to get it cleaned up for a better look. I appreciate all the input and ideas. I'll post photos when I've gotten the gunk off. In the meantime, if anyone comes across something similar, please do let me know. Thanks everyone for the help. Mystery pieces are more fun when you have someone to share the mystery with. :)