Hi Kathy - Good for you for getting things organized. I will add a caution - check the safe deposit access laws in you state. My uncle had done the same, giving my Mom a key, but when she went to access the box, the bank had frozen it based on his death notice (they were joint holders) and she had to get a probate judge's order to get access even though he didn't have enough assets to require probate. We have elected to keep items in our safe at home for this reason, and our daughters know where they are and how to access. When my Mom was in assisted living, all of her important papers were in my sister's and brother's possession. The alternative would be to copy all the items in the box, seal them in an envelope and give it to your sister.
Sue