I don't know I have ever seen one of these from these years without a passenger side mirror. https://newyork.craigslist.org/wch/cto/d/maryknoll-1980-lincoln-continental-only/7195953804.html
I would have thought they'd have been included by then, but I recall seeing a lot of lower end cars at the time still had it as an option. Although if you look at the factory brochures for these cars, the right hand remote control mirror was a standard feature in 1979 but was listed as optional for 1980. It wasn't until 1982 that they list both mirrors being standard features.
Omitting the right side mirror may not have been the thing to do for safety but IMO that Mark sure looks elegant withhout it.
Down to $7900. Claimed 26k miles. https://newyork.craigslist.org/wch/cto/d/maryknoll-1980-lincoln-continental-only/7234617704.html