This section of the Lamington River is known as the Black River. I'm not just making this up, you will see the name used in businesses in the area (Black River Coffee Co.) and on signs in Hacklebarney St. Pk. It is a very pretty run. It is also very small and creeky and can be a long day if you do the whole thing from Coopers Mill to Pottersville.
Generally it's a III, but with a little bit of extra water some of the tighter drops could easily be called a solid IV. This creek also picks up a lot of wood at times which can add to the difficulty/danger and slow down your progress. The run has two small gorges. The first is upstream of Hacklebarney, the second is just above Pottersville and is very narrow (it starts just below a small summer home on river right). The second has only two rapids, but the first of the rapids (Nasty) is quite tight and would be a solid IV+ with 3' on the gauge.
Here's a video of some of the drops from Dec. 22, 2018. I think the Level was 2.6'.
First Descent Alert!! As far as I know, Trout Brook and Rinehart Br. haven't been run!