All this mucking about with
the reels every 20 minutes means that when you're a projectionist in a
system like this, you never actually see the movie you're projecting,
just 5-10 minute chunks every 20 minutes or so.
The cabinets shown in the picture would be used to store the movie
reels, not for shipment, but for projecting.
There were larger projectors that would allow for a number of the 20
minute reels to be spliced into a larger reel (not platter), so the
projectionist really only had to do one changeover during a normal
movie. I think at those theaters these old cabinets were used mostly
just for storage for films awaiting (or just arriving from) for
shipment, since the there was very little "mucking about".
--
Will