The toggle train might not be original, but any Luger with an Erfurt marking is desirable to my way of thinking...
Now...Is it just me, or does it seem like there are way more Erfurt toggle trains than there ever were complete Erfurt Lugers???
OK; I'm looking at that gripstrap marking...My WAG is that the 3rd character is a Roman Numeral, and the 4th character is a script/cursive character...