One thing to keep in mind about safes... is they can become the carry-out box if they are light constructed and not properly anchored. A SENTRY fireproof (resistant) document safe will probably fill your needs for your coins, you will need to bolt them to the floor of frame it in a secure setting. With safe you want to make it a "slow go" with thieves where the time spent trying to remove it from the location overrides the benefits with in.
Also the less you advertise wealth, or valued items the better it will always be ..Op SEC is number one.
The safety deposit box option is always a viable option, for coin and wealth storage. But there are disadvantages with them. They are not under your immediate control, you have to plan to go view the contents (add/remove) and contents are always subject to government seizure. Ask your grandparents what occurred when the government made Gold ownership illeagal. The Deposit boxes were seized of contents and inspected for Gold.
I'm a fan of the larger heavier gun safes, secured to the floor maybe concealed in a hideout room, or placed in the basement as a new home is built. It will provide a wider range of use for valuable storage. But you have to use them as designed ask any gun owner on any forum that have large safes with their guns. How many leave the doors unsecured when they are home, or fail to check the door before the leave the house for the day? lol.