1403 prior to 1403N1 used a chain. Plastic band with imbedded type slugs. Not user modifiable. The thing that held it in the printer was user replaceable. The N1 used a 1416 train cartridge. Also could be swapped by the operator. It had a gate that could be opened to remove/replace a slug. Looks like a CE would have to do it. https://tangiblemediacollection.com/_images/typewriter-font/ibm-printer-chain/ibm-printer-chain-5.jpg?ver=1661774460
The CHM 1403s use chain devices. They are paranoid about what they print in case they break one. The plastic is 50+ years old. No OEM replacements around.
