The hinges are a two piece design, and they come apart by gentle pressure upwards. That way the whole door can be removed for, well, whatever. The offset is achieved by the small plexi block you can see behind the hinge piece on the door, thereby setting the hatch back into the slots. Every bit of it is built with 1/2" tinted acrylic, and those four hinges. Look closely at how those hinges are offset by those blocks, it's really very simple.
Oh yeah, Fisheries Supply carries those hinges.
One more thing. To get that edge, sand them down very smoothly, I mean slick. Then run the flame from a propane torch back and forth very quickly and you end up with that polished edge.
Update. The Olson that started this thread is now racing and cruising in my fair city. And just last week a dock neighbor replaced the OEM smoked plastic clear sliding hatch on his pristine C&C 99, with a new piece of light smoke tint plastic (probably acrylic, but I did not ask). Looks terrific, and he's delighted not have a UV-damaged and scratched lens to look thru anymore.
We have thought about replacing our home-made one piece composite hatch board with a clear one or better yet a hinged two piece one. Too many other things on our "list" for now, but it's getting closer. More light on a rainy day would be really nice.
There have been several good hatch lens replacement reports lately. Rick R. takes on Lewmar Rollstop hatches here. I found this video adds a bit to the critical procedure of finishing the visible seam where the acrylic joins the frame. My older...
The one-piece hatchboard has been a success for offshore, and the storage works well.
Some things you never get used to, and of course we all never get used to different things. For me, it was three- or (arghh) four-piece hatch boards. I know it's tradition. Yes, they're sort of easier to store. OK, they permit ventilation...
So far I've been happy with my 4 piece acrylic dropboards. They're all interchangeable with the teak ones so they can be mixed and matched. Had leftover acrylic from the hatches. Cut with a router. Used teak u-channel for the edges. They stow easily with the wooden ones. Sure brightened up this rainy day.