How do you find out if a deceased person had a safety deposit box?

My grandmother recently passed away and my sister and I are in the process of sorting thru her assets. I believe I remember her mentioning a safety deposit box in a small town in which she used to live. However, I am unsure of how to find out if if she still had it at the time of her death.

Although I haven’t tried, I suspect that if I just call up the bank out of the blue they would not be inclined to give out such information to a total stranger on a cold call (at least I would hope not).

Also, I believe her mentioning having some mineral rights to some property but have not found any papers to that effect.

Is there some sort of procedure (other than the unclaimed money database) to find out about a deceased persons little used bank accounts, safety deposit boxes, all but forgotten real property holdings, insurance policies, etc…?