From the photos of the eBay mirror, I fail to see that mirror as being side-specific.
Not sure of your mirror from the photos. Black paint tends to obscure things.
I am thinking that most OEM mirrors would have some sort of casting or part number on them.
Therefore, I'm guessing your mirror is one of a pair of aftermarket mirrors of the period.
There are original and repo Mustang sport mirrors with a very similar shape. Driver's side is remote cable-controlled, with the RH being manual as is yours.
http://www.mustangsplus.com/xc...H-Racing-Mirror.html
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