Hello. Just seeking advise please on helping to identify a vintage motorcycle frame Im guessing from the 1920s or 1930s. Has frame number G4 / 571 or GA / 571 stamped on front tube just below steering tube. Possibly Excelsior or Sun ? Please see photos. Bike has a Villers 250 cc 16A motor and thanks for advice to date.
Also attached is photos of gearbox on bike which I am trying to identify. The box has a ‘G’ at the bottom and number PB 978 or P13978 but no brand name. Can anyone tell please what model / year / brand gearbox it is. Thanks