Bolt, 5/16in x 1in x 26tpi, zinc plated. BSCY / CEI with slightly domed reduced head 1/4BSF (7/16 AF), Norton AJS matchless Triumph style pre 1960s.Original part number:22475; 067805 - bolt, silencer fixing bracket 1960+E6165 - oil tank platform pin, oil tank bottom bracket plate bolt