Hello, Norman and thank you for your question.
I know, sometimes it's difficult to read the model number, but is it TC8-331, instead of TCB? If so, here is a downloadable copy of the owner's manual, which gives instructions on how to replace the batteries:
If the four-bitted key that came with the safe was to be used in conjunction with the electronic combination, was misplaced by the customer, there was also an 'override' (skeleton) key that was attached to the owner's manual, in a plastic bag. If the override and/or other key was lost, then, the customer can order a replacement key from Sentry, directly, by following directions at this site:
I'm assuming the customer knows the combination, but if that has been misplaced or forgotten, as well, it can also be retrieved from Sentry:
If you need to speak with a representative, here is the phone number and hours:
Monday - Friday, 8am - 6pm EST
US and Canada Customer Service Center:(###) ###-####/p>
I hope you found this information helpful and if so, please let me know, here and/or click on a positive rating so I am credited for my assistance.
If you have any further questions, please reply back at any time, at no additional charge, even after rating.
I wish you much good luck with this customer's safe!