The early 20th century restorer had reinforced the soundboard with gluing walnut (very thin) veneers from below the soundboard to laminate it.

Laminated soundboards existed (we know at least from 1770s by Carl Lemme and later in the 1830s in France) but here we removed these 20th century veneers with a bit of humidity and fast removing by hot gun without affecting the soundboard, then cleaning the rest of bone glue.