from PROFESSIONS DES COMMERÇANTS ET INDUSTRIELS DE LA VILLE DE PARIS 1914
In the 1914 directory Dounovetz was just a seller of "toutes marques", but the 1921 directory shows marques "WD" and "LPV". Cards with the WD marque had already appeared during WW1, printed by Etablissements photographiques de Boulogne-sur-Seine, which produced cards for a number of different publishers.
from ANNUAIRE DU COMMERCE DIDOT-BOTTIN 1921 PARIS - TOME II
Comparison suggests that these logos were individually painted on the master of each card rather than using a transfer.
WD Paris 1209, posted 1916
WD PARIS 1313, posted 1920
LPV 543, posted 1921
