It was customary for the Broadwood firm to mark the maker's number on the belly rail, wrestplank, stand, and music desk. Pictured below is the maker's number, 3448, inscribed in pencil on the lower belly rail, stamped on the top of the front section of the stand, and in ink on the bass section of the wrest plank. (Click on images to enlarge.)
The desk for this instrument, however, is stamped with the maker's number 1622.
Unfortunately, instrument number 1622, built in 1799, does not appear to have survived.