You mentioned first that the BMW stamp is missing. But I see you have removed it now.Nice mirror
In the ‘80 these mirrors were also used on the Mitsubishi (with Mitsubishi stamp )
Nowadays you can new mirrors
e.g. https://www.loentje.com/shop/bmw-02/exterieur/chromen-buitenspiegel-links-bmw-vanaf-1973/
Used on the e3, e9 e10
I checked on tree of my cars. They are all similar. So in my opinion yours is original.You mentioned first that the BMW stamp is missing. But I see you have removed it now.
Do you mean that the mirror is aftermarket?
Can you show me a picture of an Original mirror?
There is no number on it, so o think it’s a reproductionIs that a reproduction or Original