A chair will tell you its whole biography if you turn it upside down. Most people never do — they sit on it once, wobble politely, and walk away from a hundred years of honest work.
The ten-minute inspection
Look for tool marks under the seat: hand-cut joints mean age, uniform machine cuts mean reproduction. A repaired chair is fine; a badly repaired one is a project. And a little worm, long dead, is history — fresh dust beneath the holes is a plague you will take home to your whole house.
Then sit in it properly, for a full minute. The best old chairs have been comfortable for a century. They are not about to stop.