That's definitely a 400F oil pan, the pump pickup thingy fits to the big hole.
Agreed that those chips look out of place. If they're steel I don't have any good theories. Alloy shouldn't curl like that but at least steel could cut alloy cleanly. I can't think where a sharp hardened steel edge would meet a soft steel surface in the 400 engine.
The hardened piston ring material could cut the iron sleeve and ductile iron does make tiny curled chips (and a lot of abrasive powder/dust) when machined?
Maybe the cam chain pivot? clutch?
Find out what the metal is. If magnetic, check compression as any sleeve gouge that made those chips would kill it. I would also look at the clutch assembly and throwout mechanism.
Since you have the sump off you can at least look up inside and see if anything visible seems damaged.