Shimano products have a date code, you can use that to figure out the year. XTR levers appear on GF bikes around 1992
Mombat has all the GF specs from 84-93. Upon closer inspection, the Rockshox showed up on steel bikes around 1993, so yours might be at the end, or not on the chart if it's later. My best guess based on spec as it appears is 93 Procaliber, based on Mavic 231, Rockshox, and XTR brake levers http://mombatbicycles.com/Fisher_Specs.htm