Starrett 12" Combination square.  Protractor head marked L S Starrett Co Athol, Mass U.S.A. no. 12.  Both heads have rust and level vials in both are wet.  Blade marked L S S Co. Athol Mass USA Hardened No. 4.  Ruler has some rust.  This may not be what a machinist wants, but square is dead nutz square if cleaned up would be great for woodworking or whatever.