It's the Pro-Ject 9cc Carbon tone arm. There isn't any suspension. The bearing and tonearm are mounted to the top plinth. The motor is mounted to middle plinth to reduce transferring vibrations to the top plinth. Also the middle will have 25-30 lbs of lead shot.
The platter is aluminum with 3 lbs of lead shot loaded in it. And yes the top (1/4" thick) is delrin.
Here is the pocket for lead shot in the middle plinth.














