Hi David... The attribution to Leonardo is far from done... The positives are we have a contemporary copy of Isabella based on Leonardo's famous sketch.. From my own research I knew she had an unusual right from that Cartoon but it hard to tell since most assume there was damage or pentimenti involved... This painting shows clearly her unusual right hand.. Just as the large contemporary copy of the Last Supper done by Giampietrino shows Christ with a syndactyly Left hand confirming that Leonardo depicted Christ with a syndactyly hand (webbed)in the original.. The swamp will be cleaned as Leonardo planned for the Pontine swamps in Ostia... best ben