what is the difference between a 2 door sport coupe and a 2 door holiday hardtop?

 

Just what you said holidays are hardtops. Sport coupes have a post.

 

The series 77 is called a sport sedan(post), and series 87 is called a holiday coupe(no post)!

 

https://classicoldsmobile.com/forums/71580-post17.html

By definition, a coupe has 2 doors.

Olds called it Sport Coupe. Generic name was Coupe.

Like a 2 door Sedan, the window frames are part of its doors.

Olds called it Holiday Coupe. After 1955, the generic name was 2 door hardtop.

Windows roll down like those in a Convertible, hence the generic name "hardtop convertible". Soon shortened to "hardtop" then to 2 and 4 door hardtop, in 1955, when the "4 door hardtop" was introduced.

Norm