Let me try this number: 201 128 1F 609 974
201 = chassis type
1 = diesel
28 = model type
1 = LH Drive
F = ???( shouldn't this be "2"?, stands for automatic tranny)
609974 = serial #
This is the format used between 1960 to 1980 except the "F". Are you sure it is the letter "F"? Regardless of year (between 1960 to 1980) of manufacture, each model was numbered consecutively, making the six digit serial #.
Does this make sense to you? This is as close as I can get. The information may not be right but you may be able to combine these with other information you have to make some sense out of it. Let me know what you find out.