In the past, I slighty converted the finecast "SM Librarian in TDA" model. Replaced his right hand with a GK one (with GK Shoulder Pad) and... a Nemesis Warding Stave
Very happy right now with my selection. S6 is nice (it's S8 with Hammerhand, enough to crack rear armor of most tanks) and AP4 does not bother me. The need to upgrade my Stormbolter is only a nuisance (yeah, able to take combi-weapon, but I do not feel the need for that).
But, as I had not use the open book on the back of the model, I would like to use it for converting another Librarian from regular GK Terminator. Any ideas how to clearly mark the model as a Libby? What do I need to add to the "stock" terminator to turn him into a chapter's Librarian?