Getting parts for our favorite 50's and 60's games that wear out with time are slowly getting harder to find. I rely on Steve Young to stock parts for my games or restores but he has mentioned more than once in the last two years that I am getting the last of a particular relay and he won't be getting more or he needs to check with say Multiproducts if they will make as parts are gone. I was unable to get a couple of popular springs for baseball games as the stocks have run out probably permanently.
So keep your old rare relay cores as you make soon have to get them rewound as one offs. Order multiple baseball springs if you ever find a stash and keep a few plastic baseball bats as some examples.