Hello to all, I have a brass or bronze piece about 8 inches long. On the front it is inscribed "Clino Mortar MK 1V, Reg No 1947". On the bottom right corner it is inscribed B I Co LTD 1944. It has what I believe are degree markings going from zero to ninety. These degree markings are marked along a curved half circle. In the middle of the half circle is a moveable piece with a buble in it. Can someone please tell me what I have here? Thank you. John