Five-color, four-territory, two-issue, registered 42 Rpf. cover incoming to Mondorf-les-Bains in 1941

Sometimes a cover is so visually compelling as to be irresistible, depending of course on your sense of philatelic beauty.  For me, this stunner was such a cover:

Mixed Franking	3 Rpf.   Alsace Hindenburg (brown) 5 Rpf.   Lorraine Hindenburg (green) 6 Rpf.   Reich Hitler-head (violet) 8 Rpf.   Luxemburg Hindenburg (orange) 20 Rpf. Lorraine Hindenburg (blue)
Territories	Reich, Alsace, Lorraine, Luxemburg
Routing	Hayingen (Lothr), 29 September 1941 to Bad Mondorf, 30 September 1941
Rate	12 Rpf. 20g letter to Luxemburg 30 Rpf. Registration fee

Validity

Hindenburgs: 1 Oct 1940 – 31 Dec 1941
Hitler-heads:  1 Aug 1941 - 1944