I don't think this is a scale, it looks an awful lot like an otolith, which is a calcium carbonate buildup from inside a fishes head. These are often used by biologists to age a fish similar to counting rings on a tree.
I still don't know what species would have one shaped like that but it may help you to look in better places to identify it.
How far northwest? If close enough to lake Superior, maybe a lake whitefish. If not very close to lake Superior or other deep lakes, possibly a white sucker or quillback, which I grew up calling a sheepshead.
Scroll through this and you can check out the whiter fish with larger scales.