Hi all, just retired from mechanical engineering background, and decided to have some fun with vintage bicycles, so I've bought a 1937 sunbeam Royal tandem, I was told the the gears, 10spd and brakes were 1977 vintage, I cannot for the life of me find a serial number, I've checked rear dropouts, bb,s seat flanges, down tubes, any information, of any kind would be greatly appreciated, thanks in advance, Jim