Outside rear view mirror

[x66 714]

I have an outside rear view mirror that looks like the 68/69 replacements except it's smaller. It measures 4-1/8x 2-7/8. The glass says
12 DMI 1. Could this be an original from the factory mirror? Were the replacements possibly bigger or is this off some other GM car?
Thanks, Joe

[bertfam]

12 DMI 1 is a mirror manufactured in December of 1971, so it's not original to your car.

Ed

[x66 714]

Thanks Ed