Dug a Bowl

A few months back on a rainy day I was walking around downtown and hit up the hills of dirt the construction crews had been building for several months as they tore up our town's historic Muskegon Avenue.
I'd scaled the faces before and had brought out a Petoskey stone-- our state stone, which is a fossilised coral-- and a paver, as there were many pavers buried under the street for a century, which I had been removing the good ones of.
See here for pavers: http://www.collectorsweekly.com/stories/177403-pavers-we-dont-have-a-section-for-em

But they had dumped more in, and I saw part of this in the dirt/debris at the top, so I dug it out and carried it back to my car with a marble, before walking down to the park and then museum as the rain increased.

My mom totally hates it, but it is kind of interesting and has what is like a thin ledge of a tab inside stuck in the rust. I assume it's been under the street for a number of decades, and I'm wondering this:

When is it from? Is it possible to ID the maker and style? What is it properly called?
Is this enamel over steel, as it is metal under there?