There are 2 main OpenSCAD objects here.
- Sight Aperture - an aperture with a smaller middle aperture inside.
This was made so that you can look through the middle aperture and keep focused on the gold itself through the shot rather than trying to put a pin on the gold.
- Sight Ring - this is effectively a customisable washer that can be modded to fit inside an existing sight aperture to narrow the centre hole