Contrary to what everyone thinks this medallion doesn't have to be from a car at all . Because none of the Mercury symbols have the large extended wings like this post and the helmet is not as large as it is on Mercury car logo .
However it might have came off some Indian Saddlebags , because of the rivet holes . Actually it could have no ties to the Mercury car or Indian motorcycle at all and but from a Mercury Boat or Snowmobile ... it's hard to locate any pictures of badges like this . IMHO , Woodstock