The easiest and most cost-effective way to open a Sentry safe without the combination is to contact the company with the model, serial number and a notarized ownership form. Sentry can look up the combination for that safe and send it to you.
The Sentry website provides a form to request a lost combination. As of 2015, Sentry also charges a nonrefundable $20 fee. It may take three to five business days for the company to process the request and provide the combination. The request can also be expedited for an additional fee. Expedited requests are processed in one or two business days.
Sentry also provides a service that allows you to register your safe and combination ahead of time. If you have registered for MySentrySafe, you simply need to log in with your username and password to retrieve your safe's combination. However, if you have lost your username or password, you need to provide proof of ownership and pay the fee.
You can also hire a locksmith to open your safe. Opening the safe is usually done by drilling a small hole in the lock, which is then repaired. This is a less-reliable way of opening the safe and is more expensive than requesting the combination from Sentry.