Decades ago, adjustable black Aristons were rumored to have been built by Koni in Europe. If true and they adjust like older Konis, they are tedious to adjust. Demount the shock, remove the spring, remove the roll pin that retains the shock top to the shock rod. Unscrew the top from the rod. Then carefully collapse the rod into the shock body until it won't move down any more.
With a small wrench, swing the rod around while pushing down a bit until you feel it engage 'something'. The inside end of a Koni is a fork that engages recesses in a movable ring. Once the fork and recesses are aligned, the rod should drop a bit further. Now turning the wrench while holding down on the rod, you can shift the damping adjustment ring. I think there are possible 4 positions. Because of the amount of wt in back, I used to adjust one notch stiffer in back than in front.
To go further with Aristons, Pat Mical in Tyngsboro, Massachusetts used to thread stock steel Ariston bodies for a Koni adjustment nut, thus turning them into height-adjustable coil-overs. Pat runs 'Performance Auto Technology' at (978) 649-2211. Remember, Eastern Std Time zone. Tell him we haven't forgotten him.