I am going to be a bit anal and picky here. I want to clear up a common misconception about reels and spools.
The above terms can be interchangeable. However strictly speaking the "reels" are the actual film itself wound on to a cylindrical
device ie: a film bobbin.
Spools are those things that hold the reels of film for projection purposes.
So a 6 Reel film will be mounted on 6 Spools.
Notta a lotta people know that. hahaha !
Dave Hardy.

In a Non-Rewind Film Platter system the plates feed and take-up the reels of film.
A Tower- system uses very large Spools to feed and take-up the film.

An easy mistake that folk make, remember when your features were 7, 8 or 9 reels supplied on 4x400' spools.

You are spot on there Hugh. It is an easy mistake and is very common place. hahaha !