That's great finding a set of nice keys. While I was cleaning and replacing belts I noticed keys would not come out so easily so I left them alone and just cleaned them while being on. I would use extra caution when putting new ones on as the plastic is 30 years old and can be brittle
![Wink ;-) ;-)](/forum/styles/default/xenforo/smilies/boomboxery/wink.gif)
Good luck