[glend (Glen)]

Michael the black ring the runs around the centre of the primary is the collar that the baffle tube screws onto, on mine there is a thin rubber gasket that sits between the centre edge of the mirror and the collar, I think all the GSOs are the same in that regard. The bright bevelled primary edge, which is done to prevent edge chipping into the mirror surface, I would blacken with a marker pen but you will need to remove the primary to do that, not everyone is confident with doing that.