The California and Ohio plants used slightly different VIN numbering schemes in 1959
, hence some confusion on late 1950's VINs.
was the first year California used the "trailer length /bed type /sequential number" format on all their trailers, although some late 1958
models had this VIN format too. Your VIN 24 D 0170 means 24 foot trailer length, double beds, 170th 24' long trailer built sequentially. The 0 before 170 is zero in a set of progressive numbers, not an alphabetical "O" for Ohio and not a zero denoting 1960
California kept this VIN format for 1960, and only the higher sequential numbers ("0226") would distinguish 1960 model year California trailers. We have not yet discovered the 1959/1960 cut-off numbers for different length Calif. trailers, so do not have any 1959
production figures. 12/58 is the correct build date (month/year) for your 1959 Tradewind.
By contrast, Ohio did not list the bed type in their 1959 model year VINs but used "9" to denote the model year. 1959 Ohio Tradewind VINs range from 24 9 001 to 24 9 187, for 187 TWs built at Ohio in the 1959 model year.