Udo, have a look at the battery in Fernando's first picture; doesn't it look like the system of a removable face is the same as in my lock ? 
Concerning your beautiful pistol, i go back to Lavin's work, in that he shows the 'extreme' solution for removable battery inner faces. 
 
 
.
		 
		
		
		
			
		
		
		
		
		
		
		
	 |