One side: 6IN. DIAMOND D DROP FORGED STEEL (Logo is D in a small diamond)
Other side: 6 IN. DUNBAR DROP FORGE CO CHICAGO U.S.A.
Looks old. Plain steel. Hex style jaws. Hanger hole is not reinforced.
According to the 1921 Automobile Trade Directory, they were located at 2506 W. 21st Street, Chicago.
Any thoughts?