It breaks down a bit like this
Pre-90 - Bontrager Off Road (OR) - just a single frame available. rivetted cable guides and seatstay/dropout interface. 1" head tube, gussets to increase strength in key places.
91-92 - Race OR - development of off road frame - rivets replace with brazing at some point 92 onwards
93-94 - Race OR and Race lite - main difference was race lite had milled head tube to reduce weight further. two piece seatstays
95 - Race OR and Race Lite - Trek started getting involved and seatstays moved to a one piece design. front mech roller disappears as top pull mechs now available.
96 onwards - Privateer introduced, Race OR and Race lite continue unchanged. Privateers built by Trek , Race and Race lite by Bontrager in Santa Cruz.
99 - Privateer moved to 1 1/8 headtube. Last year that bontrager frames produced.
The 97 catalogue said that a Privateer was "99% of the performance at 50% of the cost". Having ridden both, I'd agree with that. All the frames are great to ride. The Race and Race lites have some of the cool features that bontrager was known for whereas the Privateer was (by its nature) more of a mass market frame.
Some one here had a quote (
@sinnerman ?) from Trek that said the privateers were some of the most expensive and best steel frames that Trek had ever made. Its wrong to think of them as re-badged Trek frames, they were bontrager frames, made by Trek.