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.