It can be "completely" restored and refinished. And yes, it would be durable. You can finish it in any way you like, whatever level of gloss you like.
Matching it might be harder than refinishing the whole thing, but with the right materials and work it could be done with little to no trace the area was refinished. Personally, I would need to have it in hand to say how I would do it.
I would be happy to buy it from you for a reasonable price if you don't want it and don't want to do the work. I prefer the ones with Fellini style locks, and no strap or pouch, but this would make a good case to carry. I don't have one in 2X4. I collect the 1x2 ones with the old style lock and no strap or pouch. They make great storage cases as well. I have padded cloth pouches for them, so they stay pristine.
I even have a case to put a 2x1 in, with a pouch on it, so it stays nice and has storage, so I can take an expensive case to the pool hall without worry. I was thinking of making some more of them to sell, but I don't want the seller headaches. I am a buyer.
You could take it to a cobbler. They don't all take on that kind of work. There are others that do leather refinishing as well, like furniture.
They can dye, patch, restore, and refinish leather car interiors perfectly.
Of course, there is the cost, and the fact it is "custom" work and you might not exactly like the outcome if you do not do it yourself.
Keys can be found on eBay, but you have to scroll through many random keys. Just match one to a picture, and you can find the pics on the web.