It's an interesting piece alright.
If it had a lid at one time, would it be an unusual design for its lid to fit within the rim? Don't most lids fit "over" the rims? I'm not saying the design could not happen this way, just that it doesn't seem usual - in my limited experience. Perhaps it had a glass lid - protected from chipping by the outside rim? But glass lids were produced after foundries moved to side-gating? Correct?
Conversely, if this piece is a lid itself, it feels strange that the gatemark is exposed on the top/outside, betraying any sense of aesthetics.
The shape of the handles/tabs suggest the piece is designed to be lifted as is, i.e. with the gatemark on the bottom, not the top.
If this is the bottom of a 3-piece combo, then I don't have enough background to guess how the rest would work as far as design.
Thanks for posting the pics.
