I agree...it looks too short to be a Overlander to me and the O'landers usually have more windows - like one in front of the door. I would say its a 1958
or '59 TradeWind. Not all TradeWinds have the window in front of the door...check this one out from the Photo Archives: 1959 TradeWind
It's AirForum member Brad's (Flyfishr) trailer.
The windows on a CA '59 I think are typically the "clear view" but this one has the vertical bars so it could be OH built...or a '58. But it looks like it has the International globe plaque
which is a '59/60 thing. So, if I had to guess, I would say it's a '59.
As far as the "serial number" is that from the plaque beside the door or "big red number" ghosts? Because it doesn't fit the known VIN number pattern for 1959s...guess it could be a yet undocumented 1958
TradeWind with a 6XXX series VIN number, if there was such a thing??? But that is kinda odd too because 1956
Safari VIN numbers are 6300-6433 and the numbers don't usually repeat or carry on like that in another model. Hmmm...a mystery!