This is a very clean used 4.5 inch size machinist's precision solid square. Both the beam and the blade are precision ground hardened tool steel.  The blade is marked THE LUFKIN RULE CO. SAGINAW MICH U.S.A. NO. 166 - 4 1/2.  It's in very good condition, checks out square within about .0002", has some minor staining, no rust. Size is 5.5" long blade/3.5" long beam overall. Carefully used, A fraction of the cost of a new solid square of similar quality! Made in U.S.A.!