Hello. I am considering purchasing a 2517.50 from an independent seller (eLady). All they would give me were the first four digits of the S/N...9504***. First question, I thought all S/N for Omega are (8) characters? Second, they told me that they believe the watch to be produced in 1979. Does anyone know if the 2517.50 was produced that early? Everything thing I have found online state much later i.e. 90's +. Any other suggestions for questions I could ask to authenticate the piece? Has anyone here purchased from eLady before? Thanks, Matt