Angeles sets the standard for this important historical item.
PUBLIC CAMP MANUAL
1935
United States Department of Agriculture
Forest Service
Region Five
Angeles Metal Toilet Stool
The Angeles metal toilet stool has been accepted as standard, and should be installed in all pit and chemical toilet buildings. Except in isolated hunters' camps, buildings which are equipped with wooden box-type seats should be remodeled immediately for installation of the metal stool, or replaced by new buildings as necessity demands. Specifications of this stool follow:
BODY OF STOOL: 15 inches high with perpendicular front and sloping back made of 20 gauge iron, with lock joint down the back. Body dimensions are 20 inches from front to back and 16-1/2 inches across at the bottom, with the front and the back ends curved with the same radius as the top, which is 16-1/2 inches diameter and circular.
FLANGE AND PROJECTION: Flange is made of 16 gauge iron, 1 inch wide and is integral with a 3-inch projection designed to fit through the floor. The 3-inch extension is at right angles to the floor flange, not sloping in the back as above the floor line. Six, three-sixteenth inch holes, centers 1/4 inch from the outer edge of the flange and an equal distance apart, offer a means of fastening the stool to the floor. The flange and projection are securely fastened to the body of the stool.
Angeles Metal Toilet Stool
TOP OF STOOL: 16-1/2 inches in diameter and circular with 1/2-inch flange to fit snugly over the body of the stool, and riveted thereto. Made of 16 gauge iron with a smoothly cut opening conforming with dimension given under "Seat".
SEAT: Consists of two crescent-shaped pieces of 1-inch birch, the outer edges being a segment of a 14-inch circle. The blocks are 3 inches wide at the widest point. Each is attached to the top by means of three screws inserted from underneath. The blocks are so placed as to leave openings of 4-inches front and back, and 8-1/4 inches at the widest point. They are comfortably shaped and finished with three coats of clear varnish.
METAL COVER: 20-gauge iron, 14-1/2 inches diameter inside and 1 inch deep with curved sides. Has a flat flange or bead at bottom, 1/4 inch in width, entirely around the cover. It is fitted with a substantial brass hinge, 5 inches wide, which is attached by brass posts and nuts 1/4 inch in diameter.
PAINT: If galvanized iron is used, treat it with vinegar and paint with black enamel inside and grey enamel outside. If made of black iron, it should be given a priming coat of red lead, followed by two coats of good metal paint.
http://www.foresthistory.org/ASPNET/Publications/region/5/public_camp/