Terry;
I have an E grade, #10515 with "Lefever Arms Co Makers, Syracuse NY" on rib. Others from SN 20K through 46K have only the "Lefever Arms Co" on sideplates. I have nothing in the 50K range, but in the 60K range up all have "Lefever Arms Co Syracuse NY" in two lines on the sideplates. None of mine have any indication as to type of steel used, other than some with a makers stamp under bbls.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra