The mirror glass needs to be removed and I believe you do this by grabbing the edges carefully and remove from the adjusting base.

From here you should be able to see the bolts/screws that hold the mirror housing together.

Haasman

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)