The passenger side remote control mirror was first available as an option on the '74 full-size Buicks according to the dealer brochures and parts list. The mirror control knob was brought out to a small accessory panel just to the left of the radio.
Here is an eBay item for the 1245814 RH dash trim panel showing the mirror control location. Seller says it came from a '73 Electra 225.
Here is another item for a '74 dash without the mirror control. It does show the back of the dash assembly where mirror control goes.
Last edited by TODD; 01-01-2019 at 10:08 PM.
Reason: add 2nd eBay item
What has been, can be again. (Bob Wills, 1942)