Factual error: A 250-year-old sea chest recovered from the ocean floor is opened, and all its paper items are perfectly dry: the log book can be opened and read, and the letters can easily be unrolled. Highly unlikely. The chest's wood and pitch would deteriorate (salt water is extremely corrosive), and the paper should be damp and crumbly, at the very least. Even more likely, it would have become a lump of unreadable sludge.
Visible crew/equipment: Early in the episode a thumb/finger is visible at the bottom of the screen turning the timer wheel simulating a working timer that is actually just a dummy prop, a few seconds before it explodes. (00:02:39)
Answer: Perhaps s02e13, "Soft Touch." Penny Parker (player by Teri Hatcher, who would have been 22 at the time) crashes at Mac's place. She performs singing telegrams and takes Mac's Jeep to her next job, but goes to the wrong house and sees 3 men torturing someone. She drives away and the men chase her, noting the license plate of the Jeep. Penny convinces Mac to help, but she's unable to remember which house it is. Later, the men find out where Mac lives and kidnap Penny and a Serbian (a guy from the beginning of the episode), Mac follows and he reveals the bad guys' plot to kill someone at city hall involved in a drug case. The three rush over to city hall and prevent a bomb from going off and the bad guys are captured.
Bishop73