At this point, in the absence of other answers to the Mystery...and the relatively low cost for an OEM Part... It might be worth a try. The Internet GM, GMC and Chevrolet Forums are rife with Threads and Posts indicating that on some if not MOST occasions... only "The Right Stuff" will do... and that narrows things down to being either ACDelco... or Delphi. YMMV if other Members chime in with some additional ideas that suggest that throwing away what looks like a "Perfectly Good, Brand New Gas Cap for No Good Reason"... is a Bad Idea.