Hello and welcome this this forum. I was in Romania last year and very much enjoyed what I saw and learned.
My estimate is that it is worth $20 to $50 as it is and after restoration it might be worth $50 to $75. Here in the US and and Western Europe restoration to full working will cost much more than the value it will add.
You can do a few things at low cost to improve the watch. If you replace its crystal and have some one put it in the case correctly at little cost. A full overhal and replacement of the missing stem take a lot of tiem which is expensive.
Another way to think o this is that a new watch of similar quality would cost well over $100 and if yuo restore it you will have a useful family heirloom. Full restoration is not commercially sensible but may be worth doing for family reasons.