Hi Gilles,
http://forum.12oclockhigh.net/album....pictureid=1023
http://forum.12oclockhigh.net/album....pictureid=1024
Actually, the first of two Messerschmitt Me 262 A-1a/U4's carrying the Rheinmetall 50 mm MK 214 (V2) cannon was W.Nr. 111899. It first flew on 27 February 1945 at Leipheim. According to Dan O'Connell,
Production Log, (Classic, 2005), pp. 141-142, Major Wilhelm Herget flew it operationally to no avail in April 1945.
The first picture shows the original modification. The second photo shows that two white gun rectangles had been added after the nose was camouflaged.
best regards,
Jim