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Use the emergency key to open the safe (that's what emergency keys to Sentry Safes are for, to open the safe in an odd exigency when the batteries are dead or the combo forgotten, etc.)
As for the missing combo... you can get it again from Sentry Safes Inc, provided that you provide your proof-of-ownership to them (the original bill of sale is what they require.) See this page for details and procedures:
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