Advice on dial restauration/parts locations

Hi there!,
I inherited this wrist watch (along with a pocket watch that I mentioned in a separate post) who belonged to my grandpa who left Switzerland in 1912-14 (although I think he got this watch a long time after that date).

I'm trying to find a place where I can buy the crystal for it (it currently has a plastic one that someone must have installed as part of a subpar service at some point in time). I'm also uncertain if this model is meant to have a seconds hand...
The poor dial also looks like it's seen better days, but being a complete neophyte in watch making, I'm not sure how or if this can be cleaned/restored.

Thank you to anyone who reads this and specially to anyone who can provide some advice on the maintenance part and maybe even a trustworthy place to source parts from😀

So, it is from around 1953. Has a second hand. For the information about the crystal you need to publish picture number 3 ;the writing inside your case back. The numbers there are important. Easy to service and robust movement. The dial ? Depends on your taste. Family heirloom? Keep the history as is. Can't look at it without a lump in your throat? Have it repainted. The very fine printed original minute ring will not come again as good as the original. Start with a new crystal and any fitted second hand ( can be cut to the correct lengths ) and a movement service after all these years. Report back with the 3. Picture. Kind regards. Achim

Hi Achim!😀 Thank you for the super swift reply!
Thank you for the recommendations on the dial. I think I'll probably leave it as-is rather than having it repainted😀 The readability is not great, but I think it's mostly due to the plastic dome being pretty garbage😀
I did check the back before posting the previous pics, but there doesn't seem to be much in the way of extra info other than the back cover being stainless steel (in French)... But there seems to be a VERY faint "3664" scratched on in the back (not sure if that's of any use). Other than that, by measuring the diameter of the plastic dome, it seems to be 31mm: