Thanks for your help. Of course, I've tried ATCC, DSMZ and other internet
based strain collections before, but I could not find anything (but: you
can't get BL21 at ATCC or DSMZ). I contacted someone who worked with the
strain but he told me that the strain was brought to the lab by someone. I
did not went back through the whole history of these bugs, and I don't
think I will. Roche uses the strain to produce a recombinant protein, I
have contacted them to, but no answer so far.
I will follow up the NovaBlue suggestion and I will contact the Yale
source, although I could not find a trace of this strain on their web page.
I something comes up, I'll let you know.