This is all a matter of your bank's procedures, however, if you're looking for best practices, and liability limitation, then I would recommend -
Yes, the customer ALWAYS signs when accessing their case (how else is their signature verified to the contract?), and you hit the access ticket with a date/time stamp.
Yes, the time of exit should always be noted, and initialed by the bank employee who cleared the viewing booth and assisted the customer with returning their case to the vault. Having the customer sign is also a good idea.
I would re-iterate to anyone who has access - that David McGuinn's Safe Deposit Box manuals are a pretty invaluable tool and if BOL ever does a webcast with him, I would certainly sign up for it if your bank has safe deposit boxes.
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My comments are absolutely no reflection of, nor influenced by, my employer - take them at your own risk.