<VV> Can you identify this mirror?

[James Cooper]

http://www.flickr.com/photos/cooperj123/
This mirror was on my 1965 Corvair Sedan when we bought it.    I don't know if it is for a full size Chevy or if it is an aftermarket mirror??    The mount holes on the car were in the right place for a stock mirror and bracket but there was an extra (third) hole drilled to mount this mirror.  Can anyone identify what it is?Jim