If you had the hydropneumatic suspension, with a couple people in the vehicle and you turned off the vehicle and got out of it, you would see the car slowly lower itself after about 2-3 seconds. Also if you see springs, then you know you don't have it. Hydropneumatic suspension uses hydraulic fluid vs. nitrogen as your components for ride stability.
I was just wondering Benzman, cuz my '84 500SEL Euro DOES have it. Maybe yours only has it on the rear suspension.
84 500SEL EURO 87K
85 300D 267K (and still goin' strong)