For what it's worth: I have the machine of Skyblazer's 1st post as "Gastambide-Levavasseur GL-2 of 1919", and the other machine as GL-1.
(For the references Gestapo: source is Dan's hard disk, as usual)
Aviafrance also dates this "GL-2" as 1919, without mentioning any GL-number:
in https://www.aviafrance.com/aviafrance1.php?ID=10053&ID_CONSTRUCTEUR=1520&ANNEE=1919&ID_MISSION=0&MOTCLEF=
hth.