...whether or not it was an old kit or scratch-built? The decals appear to be a commercial set. This is the only one that I have seen in all my O years. Note that I installed the Athearn metal Andrews trucks as I like Andrews trucks. A photo of one of these cars (MON 6464 lettered for WARD STONE QUARRY on display outside of their quarry) shows it on Bettendorfs.
Note that I should have taken an underside photo when I took these! Anyway, it has become one of my favorite cars.
BTW, Aluminum Ore Co. was a predecessor of Alcoa.