Yes, many years there were several framesets that were identical. In '92, the Trek 950, 970, and 990 used the same exact frame, but used different forks. The 950 and 970 used the "Big Fork" while the 990 had a suspension fork. That same year, the lower-tier 930 had ALMOST the same frame, except that only the head tube and top tube were OD. Then the next year, 1993, they gave the 930 the same frame as the 1992 950/970/990. It worked that way for a while - identical framesets in the higher-end models differing only by the fork and (of course) the rest of the components, and the lower-end 930 usually got the higher-end frameset from the previous year. This isn't absolute in all years, but that was the general pattern.

No matter the model or the year, they're all full DB chromoly with great geometry and are fantastic frames. The specs are all available for comparison out on the Vintage Trek site. You can download the manuals.