The lens boards for the Graflex 23 cameras, both Century Graphic and Speed Graphic, are rather special. They are stamped aluminum, about 3/64 inch thick, 2-1/2 inches square, with rounded corners. They are dish shaped, and the part perpendicular to the lens plane forms a light trap with the interior of the camera. It would be difficult to duplicate them. These boards were once common, but they are now hard to find.