When changed the S/42-code into 42 ??
 

I read about the code change from the older S/42-code to the newer 42-code, which took place in 1940.
Now I was wondering, when it changed exactly? Is there any suffix (lets say "k") that had the last S/42-code and the 42-code began with the "l"-suffix, for example.

Can you answer me this question?

Karmast, the last S/42 is a 1939 in about the Q-Block Suffix. The earliest Code 42 is also a 1939 in the late P-Block Suffix. There is a little overlap. Hope this helps!

yes, that helps! thank you very much, frank!