Nice big old enamel ware bowl - this holds about a gallon, and measures about 12" across the rim, 5" deep. It's probably 1930s or 40s vintage, not marked with a maker.
This looks like a Cream City piece to me - quite heavy, with the classic Cream City blue with black band. We find a lot of vintage Cream City pieces here in Wisconsin!
It's in very good condition for a piece of this age and type, some light scratching and wear, clean without serious staining.