Hi Stig,
You are right and for a non-French you have very good knowledge of the French Air Force.
Congratulations
The MM in W were Caudron C275 Luciole, Caudron C600 Aiglon, Mauboussin and Salmson "Cri-Cri"
W-515 is Matricule Militaire for I think a SALMSON D6.T2 CRICRI
For example I have
W479 Salmson D.6 Cri-Cri n°102
W550 Salmson D.6 Cri-Cri n°164
another view of this same a/c proposed by Ed some weeks ago
https://www.ebay.de/itm/325403503210...Bk9SR5jiyt2EYQ
Bertrand