OEM is not just a reference to metal moulding.
It originally , as others said, meant Orig. Equip. Man..
For instance, on your car, you want to get OEM parts. Not knock-offs.
For metal mldg it originally meant the profile that company "Y" is making is made to the same specs as company "X". "X" being the original manufacturer.
Now it has come to be used as a reference as mldg only avail in quantity, and to certain accts.
Framica does have several OEM lines avail. if you purchase in the right amounts.
Later the open it up for general use. If it is a dud for the OEM purchasers, then it will go no farther.
Many companies are using the term Box Moulding too. OEM and Box can overlap.
For instance:
Universal's N1510 or N1210 might be considered an OEM design. Buy it by the box and pay less.