 Marlon Brando (qv)s motorcycle is a 650cc Triumph Thunderbird.  From stills, its registration number looks like 63632.  Lee Marvin (qv) himself also owned a Triumph, a 200cc Tiger Cub  upon which he competed in desert races. Gil Stratton Jr (qv) was  featured in a print advertisement for Triumph motorcycles in 1963  and in his later, more respectable identity, was a famous sports  announcer in Los Angeles for decades.