Many designers, big and small, of that time used this ETA 251*. This bodes well for you in the event that it needs any parts should you ever have to bring it in for repair. I worked on one a few weeks back and was able to find new old stock parts on "the bay". Some watches aren't so lucky.
Your inheritance is a simple, but rather elegant ladies watch, to my eye. And there's a decent amount of 18k gold used between the case and the bracelet. Overall I think it's quite nice. Enjoy it with the associated memories and appreciation.
BTW, if you take to wearing it a lot, you should strongly consider getting it serviced before doing so too often. These watches have tiny pivots that ride in its jewels, which are harder, and if/when the oil dries, or dirt finds its way in, the pivots can be destroyed in not too long. But if you're just going to wear it to Xmas parties, and the like, a few times per year, you might get away with the occasional wind-up. Still, a service, if you can swing it, and find a good watchmaker near you, is advisable.