Milling Cutter Tool Holder SJ-30546 S.J.&Co. #14. Came in an auction lot, don't know much about it. It has a 2" diameter arbor with a keyway for holding milling cutters. Threads on the inside look good. I think this is an NT50, but am not sure. Please verify before purchasing. Thw draw bar threads appear to to 1"-8tpi.