I restored a CHAIR and found MYSTERIOUS letter

The full UPHOLSTERY TUTORIAL is here: This 19 century chair is from new classicism period. In Estonia they probably belonged to German landlords or to rich merchants. It is made out of local birch and covered with black shellac. Usually there was a big set that consisted a table, sofa, 2 armchairs and 6 or more regular chairs. 0:00 Overview 0:16 Stripping the upholstery 3:38 Woodwork 07:48 The letter 09:32 Woodwork 11:34 Finishing 13:14 New upholstery 23:09 Reveal My favorite tools: Makita plunge saw and guide rail: Makita router: Makita router guide adapter: Kärcher steam cleaner: Bessey edge clamps: Dovetail jig: Workshop vacuum: Random orbital sander: Oscillating Spindle Sander