So so great...
Thank you very much, guys...
The piece was found isolated by a girl many years ago a couple of kilometres away in the East of Rethel (France).
600 meters away from that there, I have a crash site probably from May or June 1940 where was found this piece :
http://forum.12oclockhigh.net/showthread.php?t=29388
I will make researches about a Dornier 17 shot down East Rethel in May or June 1940 and find the crash site : no more direct witness!
Bon vol