Yours is a Murray built bike, from 1958 or later. If that chainguard is original, it was likely a JC Higgins for Sears. If so, it will be stamped 'MOD 502' on the rear brake arm side dropout. That was Murray's code for a bike built for Sears. There may be a 5 or 6 digit number after that, which is the Sears catalog #. Sometimes, it can be matched to a specific year. -Adam