+1 on the fender light.
Since JJ said it had "Japan" stamped or cast into it, probably one of the first round of "knock-offs", possibly from the late '70s or '80s.
Later than that you would expect the second round of knock-offs to be from Taiwan and the third round from China.
If it has a bulb, a 6 volt would tell us the intended application would be for about '64 and older, if 12 volt then probably around '65 or later? Something tells me that H-D changed from 6v to 12v around that time frame.