Safe enough to store valuables securely(adjective)
A safe-deposit box(noun)
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Use "safe-deposit" in a sentence
"Sitting in a safe-deposit box in a discreet bank in Geneva, Switzerland— along with ten passports with ten other bogus names on them—was his genuine passport, the one imprinted with his real name: Orville Timken."
"The man's lawyer told Muller he had a Honus Wagner card in a safe-deposit box."
"A start panel of four contestants compete to answer questions which open safe-deposit boxes stuffed with money."