What this colors mean ?

[el156]

Does someone know the meaning of this colors in the back of this transistors ?

 

[sq225917]

Looks like someone has measured them for matching.

 

[sajti]

It was selected to different group, usually by the Idss.

Sajti

 

[el156]

I bought them like that years ago, so looks like they are factory matched.

 

[Elvee]

Does someone know the meaning of this colors in the back of this transistors ?

Marking for internal use, like traceability, unpublished performances, plant, wafer, etc.
Not useful for anybody else, except if you have access to insider's information