It's nice to see Emaks turn out this way. I have always thought it looked incredible in Amidol untoned, because in most toners it takes on this pinkish quality (sulfide toners) that I dislike. The cool quality of the blue developer seems to really add a lot. (Balanced out by the selenium?)
Max, it is a B+W RG715 filter.
Thomas, the response to selenium is quite fast, so 30 seconds (1+10) are almost too long. If you see a color change (at about 45 secs) it could be too late for an interrupt, higher dilution (1+20) can be handled safer.