Early M1918 bolt assembly.  This has the Prewar style of drawing # on it; the bolt is C-9068-3 and the link is C-9072-1.  C is the drawing size (so you went to the ‘C’ filing cabinet) the next 4 numbers were the part # (during WWII we moved to a 6 or 7 digit number system) and the -1 or -3 was the revision.  So this I very early bolt.  It is in  the white and I suspect it is Nickle Steel.  There are no manufacture markings on it 

a super early bolt, ready to run