If you've finally acquired a teletype for your vintage computer, you need to replace the rubber print hammer head because it will have disintegrated. It will feel like a gummy bear candy. The acknowldeged printer hammer head replacement for the Teletype model 33 is a PVC tube, fit over the hammer like a sheath, but I have found recently that these last less than 100 hours before a the tube needs to be replaced. A permanent divot will form on the tube where it strikes the cylinder, making it useless.
So here is a tip - if you use your teletype regularly, replace the hammer pad each time you replace the printer ribbon.
Here is my Teletype 101 primer - how to set up an ASR 33 for use with a computer.