I know nothing about holsters; but its being left-handed raises questions in my mind...(Although the theory of it being a cavalry holster comes to mind)...
I do remember that a well-known US holster mfg made US marked military-style Luger (and other makes) holsters in L&R configuration some years back...Probably still offer them...
I used to have their catalog, and pics as well, but with 75 CDs full of archived Internet data, I have no idea where they are...
Edit: According to this Forum thread, Rock Island Arsenal did make hip holsters about that time...
http://forum.m1911.org/showthread.php?t=6042