An insert for a standard weight plate. The inner hole is for a wooden dowel to serve as a telescope counterweight. This is a very temporary solution for an equatorial telescope mount(CG-2) that was missing the counterweights as well as the counterweight bar, hence the wooden dowel. The next revision may include inserts for nuts to fit a threaded rod for a more adjustable weight placement.
Better version available for Olympic weight plates on my page
The author marked this model as their own original creation.