These "Imported" models were the cheapest bikes of the lineup. Probably because of that they didn't get much love in the ads so that makes tracking down the date a little difficult. Western Auto appears to have sold three different versions. This one from the 1958 ad has cantilever bars that run continuous back to the dropouts. This one from the 1961 ad has two top tubes and a single cantilever bar Or the style like yours which has two top tubes that run back to the dropouts and two cantilever bars that terminate at the seat post.