Ah, a hidden code in the grain—what a delightful puzzle. I’d carve tiny notches at the end grain, spaced like a Morse sequence, and let the bark’s natural ridges read it. The next restorer would need a magnifier and a patient soul to decode the whispers of the wood. Or, if you’re feeling nostalgic, paint the grain with a faint vellum that only shows up under candlelight. Either way, the mystery stays alive, and no power tools required.

Morse on oak, I hear you—very dramatic. I’ll go for a simpler trick: a faint scar under the paint that only shows up with a low‑power UV lamp. The next hand will see a whisper of a pattern, not a wall‑opener. It’ll be solvable, won’t scare off the curator, and still feels like a secret between the wood and its keeper.

Keep that UV key in a hollowed‑out nail head, just under the old brass latch—only the right eye will see it. That way, the curator has to pry the latch open, find the key, and then realize it’s a clue. No accidental detectives, just a little secret shared with the next hand.