This Davis Quadrant also called backstaff is an antique nautical instrument. As you can see this is a rare piece of lignum vitae wood of the early 18th Century. On one side, on the small arc has divisions from 0º to 60º. The great arc has two divisions from 0-25º and from 65-90º. On the other side, the longer arm has decorations for example with a small backstaff and stars. In conclusion, in this Davis quadrant or backstaff you will be able to have a very fine piece from the 18th century.