This is not a safe deposit question, per se. It's much more about how a decedent's estate works.
If it was a forgotten $50 savings account in the wife's name your bank would be taking $50 worth of risk in turning it over to an "heir" instead of waiting for it to escheat. However, you don't know what's in the box, so you cannot quantify the risk you are taking. I would bet dollars to doughnuts that it's empty or contains nothing of value, but that would have no bearing on my decision.
If they want access to the box their personal opinions are entertaining, but not controlling. (Nothing is less relevant than who the personal representative of the surviving spouse's estate might be.) They need to get a court order to reopen the estate and name a personal representative (anyone) for the sole purpose of accessing the box and delivering the contents according to the decedent's will. If they don't, your bank will escheat it to the state in the requisite time frame and they can make their claim against the state - after getting a personal representative appointed.
In essence, what Mr. Carey said.
In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.