This is a combination collective counterweight and cable strain relief.
It uses the 500g weight from this pack.
https://www.amazon.com/gp/product/B01IP7G3ZK
2 x M4x16 socket head bolts attach it to the side of the Collective.
2 x M3x12 bevel head bolts hold the cable strain relief in place.
2 x M3 threaded inserts
I used some paint on support for the very center of the weight opening.
The author hasn't provided the model origin yet.