Here's a case about a reel. Going back about 7 years I bought a 400ft 16mm off Ebay for 99p, someone had not rewound the film on to the original reel, and it came on a 1600ft take up reel. The film was in a shocking state and I put it on a 400ft reel and gave it to a charity shop. The 1600ft reel has UK patent numbers on it, which I looked up and found the following.
Improvements in spools for kinematographic and like film strips. 563,004. Film spools. ACME SHOWCARD & SIGN CO., Ltd., and WISBEY, S. April 8, 1943, No. 5654. The core consists of a sheet metal strip 1 provided internally with spaced bearings or guides 4 housing the shanks 7 of rivets connecting the side plates together. The guides may be produced by forming parallel slits in the strip and pressing out the metal between them; one, two, or more such guides may be provided for each rivet, and three or more rivets may be used for each spool.
The full patent is available to read online and consists of 2 and half sheets. I don't use the reel, I prefer a plastic take up reel, but it's a nice item to go with a projector I have of almost the same age.