OMG I am so blind . Description clearly states: "14/6" Lt Udet... and then "28+29"... According to this website, "28+29" means two victories: 28: 07 Jun 1918, Jasta 4 SPAD (opponent), which took place in this location: E(ast) of Villers-Cotter?ts 29: 13 Jun 1918, Jasta 4 SPAD (opponent), which took place in this location: N(orth)W(est) of Faverolles So we have 14th June 1918 (he had one more victory that day). Great. Igor, thank you very much for your comment and pictures, really - good job. Regards! ps. What is the "SPAD" ?