Yes, the 203 is the old mid/late 70's fulltime unit. The 205 is the old gear drive unit, both last used in 1979.
80-87, you will find NP208's(smooth aluminum case) and BW1345's(ribbed magnesium case,) 88-96 is pretty much all BW1356, and 96-7 has a smattering of BW 4404's. All 80+ T-cases are chain drive.