Looks like 1984 vintage; I think I see three 'dots' to the left & right of the 'SS' on the tang stamp. A knife from 1980 would've had 5 dots to each side (totaling 10), and one dot would be removed for each successive year, with only one dot left in 1989. Looks like 4 dots have come off of yours (leaving 6), hence the 1984 estimation. The 'lightning S' (zig-zag form of the lettering) was used on '80s vintage knives from Case. Knives made in the '70s would've had a similar dot-scheme for dating, but used different lettering. Scale covers do look like synthetic (delrin).
David