[Leica] Rigid Summicron,"41" scratched inside lens

[pklein at 2alpha.net (Peter Klein)]

I'm looking at a picture of a rigid 50mm Summicron that has the number 
"41" scratched on the black barrel that covers the lower portion of the 
optical cell (only visible when unscrewed from the mount).  Can somebody 
tell me what this "41" means?  The owner doesn't see any more numbers 
scratched anywhere else.

Were there really 50 Summicrons whose real focal length was a whopping 
54.1 mm?  Or does this number mean something else, like "I'm Wolfgang, and 
I inspected this lens?"  Or. . .?

In comparison, my DR Summicron has the number "19N" scratched on the black 
ring visible if you turn the lens head upside down and look down on the 
rear element. That confirms that the exact focal length is 51.9mm, as it 
should be, with "normal" color rendition.  If I recall correctly, the 
number "66" is also scratched into the same ring.

So, what's with the 41 and the 66?

--Peter