BriP asked me about a Blade Nosepiece that wasn't quite fitting onto a Blade lens. Got me wondering about the various nosepieces that we have from Blade to Modern M Frames.  
 
Blade: 
 
 
 
Slit: 
 
 
 
Zero: 
 
 
 
 
 
Odd Sub Zero: 
 
 
 
Older Style M Frame Kit: 
 
 
 
Newer Style M Frame Kit: 
 
 
 
SI M Frame 2: 
 
 
 
Almost seems like there was a smaller style just after shrinking from the  Blade/Mumbo to the Modern 'pointed' M Frame nose piece, were it was still flatter, but also smaller. The SI M Frame 2 also did away with the pointed form.