i think he is talking about a safebox in his house, he can control it easily if he know the combination
That's a horrible idea, what if your house is broken into and someone grabs your lockbox? you pry those things open in seconds with a crowbarI honestly believe my methods are the safest possible:
For my hot wallet I use my Trezor, for cold I use paper wallets and store them in a safe deposit box ( insured! 
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I also keep my recovery card in my safe deposit box
)I also keep my recovery card in my safe deposit box