I was thinking of an external pump that brought oil to the engine from a supply tank. That oil pump clearly bolts into the bottom of the engine at the flange, with the perforated bit inside, and an oil line outside, so it circulates the oil in the engine and brings in more to replenish it. The perforated bit is not a filter as we know it but intended to keep metal chunks, debris, small birds, etc. out of the bearings. I'm not entirely kidding about the birds. A friend of mine found dead mice in the sump of his 1926 Nash. They had gone in through the oil filler tube and drowned.
Presumably the documentation shows the bottom of the engine and more about the oil system. It might or might not have a sump as we know it.
What is the thickness of the metal on the fragment? It looks substantial. Do you have a picture of what was the inner side, that had be4en coated with oil?
LTM (who checks for mice at every oil change)
Don