Exploded parts diagram of a 2-position side mirror assembly

2-Position Breakaway Hi-Lo Mount Mirror
The additional arm (barely visible in the diagram below the mirror head) pivots out, shifting the mirror so the driver can see around his own wide trailer.

This rare (pre-'82?) mirror is easily identifiable by the 3-screw-per-pad mounting.

Owner caption November 2011 · Photo 3990 of 5000