Civilian went into production in 1990. Earliest version was plain aluminum with kraton inlays. Tuffram coating was added fairly early on. Spyderco started marking the steel on its blades around 1992 and originally labeled blades of GIN-1 as G-2. That changed began around '94-'95, when they started stamping them with the actual name, GIN-1. Knives made prior to '92 do not have steel type stamped on them.
For what it's worth, the handful of Tuffram Civilians I have handled were all marked G-2, so I cannot say for sure that the steel marking on them was ever changed to GIN-1.