I have just discovered this nice lancers shapka in Greece.
I think it is an Officer's 2nd Ulanen Regiment tschapka of the Austrian-Hungarian Empire.
I hope that the experts can give me more information!
indeed, it appears to be a 1905 pattern Rittmeister's helmet as denoted by the rank braid surrounding the body of the helmet. The Ulanen Regiment Fürst zu Schwarzenberg Nr. 2 had a dark green covered "mortar board".
