And the winner is...
Arnold Briggs & Stratton 1-3/4 In. Gas Cap GC-134
1-3/4" diameter, vented gas cap with liner. Fits Briggs & Stratton model No. 397974-Max. engine, Quantum, and Europa Series engines. Individually carded. Diameter: 1-3/4 In. \n Warning: Cancer and Reproductive Harm - www.P65Warnings.gov -