I have Chicago Schwinn Twinn Deluxe tandem, sort of a maroon. It has 5 speeds controlled with a lever. We have owned it since around 1987, did not buy it new. We lived in Chicago at the time and rode all over. My husband died and I will not be able to ride it. I'm trying to determine its age. I read forum postings about serial numbers. I check on the bike and it APPEARS to me to say OHO78239. It seems pretty clear but from what I read it should be 2 letters not using O and only have 4 numbers. So I am confused. If anyone can provide me with direction I'd appreciate it.