There are two achievements in Forza Horizon 3 relating to the De Luxe Five-Window Coupe:
Collector's Edition = Restore the De Luxe Five-Window Coupe
Wild Card = Win an S1 Class race in the De Luxe Five-Window Coupe
Having been introduced in 1932, the De Luxe Five-Window Coupe is the oldest playable non-fictional car to be featured in the Forza series.
The Quartz Regalia, while the oldest playable car in the series with a year of 723, is a fictional car.
The developer build of Forza Horizon 3, released in January 2017, had the Five Window Coupe's name shown as "Ford De Luxe Three-Window Coupe". This has since been fixed with the car using its correct name as of the release of the Hot Wheels Expansion.