It's been a long time since 1981. Chances are your Medusa isn't made of stone and has seen some wear.
Undoubtedly, your clear ball guides have turned a shade of yellow from smoke an UV or broken.

They will brighten your game by allowing the light to shine through and sparkle on each guides fire polished edge.

Includes two clear lane guides shipped in a protective blue film. They are shown with the original guides in the photo for contrast.

Here's instructions on how to reuse the metal posts :

https://pinside.com/pinball/forum/topic/upkick-pinball-s-latest-shop-items#post-6786370