The old man's coffin is an item obtained during the quest Making Friends with My Arm by giving him a reduced cadava potion. It is to be given to My Arm to prove he "killed" the Wise Old Man.
As the examine text implies, players cannot cast alchemy spells on him. If a player attempts to do so, the chatbox will state (You sense the Wise Old Man's disapproval.)
The coffin has a "Talk-to" option, where the player says "Hey, Wise Old Man..." and is given five dialogue options. However, as he is "dead", he will not respond at all.
- Are you actually alive?
- Can you check my bank for junk?
- Tell me some of your wisdom!
- Can I have all your money?
- Rest in peace.