O Scale 1:48
When you see a manhole in a street you see the cover and the ring that it fits into. Remove the manhole cover and you see the ring and the open sewer hole. This is one ring (normally buried up to the top in the road) and the manhole cover. There are three vesions currently with Water, Sewer and Storm on the top surface.
If you look at the example here .. the ‘rusty’ one is the Storm Drain Ring and the white one above it the Sanitary Sewer Ring. In the “real world” the top of the Sanitary Ring is the only thing most people ever see as this is the ring around the manhole cover we see in a road. The Storm Drain rings fits into the Storm Drain cover.
When printing on a MSLA printer (Masked Stereolithography Apparatus) the models are supported on scaffolding called supports. The slight texture where the supports touch the model (a few thousandths of a mm) can be left .. “as is” but I prefer to lightly sand that surface.
I simply sit the covers and the rings on an emery board .. making sure that the writing is up on the covers and that the little recess for that cover on the rings is also facing up .. them push them back and forth across the emery board a few times with the pad of your finger. That is all that is needed. Clean up, prime, paint and install.