I know the pictures are cut off. The rule's 12" in diameter. It doesn't fit on the scanner. The bits you can't see look pretty much like the bits you can.
I totally have no idea what the purpose behind this rule is; it's awfully big, and the scales are a little weird; it's got 4 scales, all on the front, labelled C (tan, cot), B (1/cos), E, and D (1/sin). It seems to be mostly for solving triangles, and the text on the front and back of the rule gives instructions for solving right and oblique triangles and the "trial shot data problem". the back also has a gridded portion, presumably for plotting triangles.
The rule seems to be made of some kind of laminated cardboard or thin plywood, and seems to operate on the same principle as the Gilson circular rule: a stationary body and two cursors. There's no indication anywhere on the rule of who made the thing or who the target user was; i'm assuming it's a surveyor's tool, but who can tell?