Hi Stig,
It would be interesting to know if all sources have a single common origin. I very much expect so. Unknowable of course but I wouldn't be surprised if the date Boiteux-Levret's death was recorded in the official records or squadron records was 24 th April, but the actual event sometime earlier, though as you point out, how likely is the photo to have been developed and posted the same day?
To be honest, this is leading me to all kinds of fruitless speculation. As an example N.2937 is recorded as being in use with N 85 at :
http://albindenis.free.fr/Site_escad...adrille085.htm in April 1917. Perhaps it was not Boiteux-Levret's aircraft at all?? In fact I am inclined to regard this as a more plausible explanation than a significantly earlier date of death. But who knows??
Regards,
Clint