I've always found less usual (for lack of a better wording) locomotives interesting to look up whatever I can of for fun at times. I have quite a collection of photos some which I have no prototype name clue of!
anyway to start with...
these two bavarian steam locomotive designs were unusual right from the start tho. even more with the central double-end pistons of the ML version
I don't know much technical details about them just yet but for anyone who would not know it the reason the coal bunker is shaped like a funnel [although the PtL's is more visible] is because its an semi-automatic firing system to allow single engineer operations. and the plates on both open end is since that made it easier to cross to or from the coaches in passenger workings (in that case I imagine it would be the conductor doing that)
heres a photo of the PtL 2/2
http://upload.wikimedia.org/wikipedia/commons/thumb/1/11/98_307_1.jpg/735px-98_307_1.jpgand a historic photo of the ML 2/2
http://www.osterthun.com/2f.models97-99/pics~97-99/98.3/4007-mf.jpgI still can't quite get myself around to as why they would build the piston and various rods in an odd location re the ML unless they must be trying to have the shortest chassis they could get away with or I'm sure there must be a better reason somewhere else