Why are different ID informations printed in the inside of the same sort of bricks? While sorting old bricks I observed that the inscriptions printed inside show a different coding. As you can see the outside it is always a ordinary "1x2 tile with groove in good old Light Gray (item number 3069)". The inside instead appears very different. 

Reading from left to right it says:

15; (c) LEGO; 032 # 
LEGO; 3 # 
(c) LEGO; 16; 35; 3069 # 
8; (c) LEGO; 032 # 
LEGO;  1 # 
3069; 36; 17; (c) LEGO # 
5; LEGO; 3; 1 # 
LEGO; 11; pat. pend. # 
LEGO;  11 # 
3069; 36; 9; (c) LEGO 


Why is that so?

You can also see that most of the bricks got on one half of the inside a yellowing. It seems that the effect is not only accruing on the surface but really eating its destruction through the material which I was not aware of.
On newer pieces (maybe also the newest of the ones you show), there's a number identifying the mold and one identifying the position in the mold, allowing LEGO to trace a problem all the way back and examine the mold if a high number of errors seem to come the same mold.