Vintage Caterpillar-style Bulldozer Watch Fob

Metal watch fob with raised relief of a crawler bulldozer with front blade and operator. Shield-shaped emblem at upper left reads "CAT"-style lettering, appears to be a Caterpillar-type logo. Silver-tone metal, possibly nickel or chrome plated, with a worn, slightly tarnished finish. Square shape with a loop at the top for attaching to a chain or fob strap; a tag with string is attached. No visible chips or missing pieces; some surface wear and dulling. Please check: whether the metal is sterling or plated, maker marking on the back, and exact age.