Don't recognize those lights, but could it also be a "dim" and "bright" situation, with ground by contact to the light post? You could use an ohmmeter to check for continuity or not between the two red wires, assuming bulbs are good. Or remove a bulb and check for two filaments....
'52 Cub ("Great Personality") 148xxx
'48 Cub with FH ("Gunny Cub") 38xxx
'57 Lambretta (a slow work in progress)
'74 Triumph TR6 (Mama's toy)