Do you remember if the nickname was "Orange Book" or was it "phone book"? I didn't see the former when searching for more information, but the latter was referenced here [0].

If it's actually "phone book", then [1] seems promising.

[0] http://www.columbia.edu/cu/computinghistory/pdp10stuff/

[1] http://www.bitsavers.org/pdf/dec/pdp10/TOPS10/1972_PDP-10_Us...