A metal protractor in a wooden storage case with lock. This is a measuring device for drawing and measuring angles. This one may well have been used by a draftsman, surveyor, engineer or architect for producing scaled plans.
The protractor is believed to be over 500 years old but its use was first noted by Thomas Blundeville in 1589. Blundeville prepared maps for navigational use at high latitudes. The angles indicated the desired direction of a ship or the location of other ships in the area. In the 18th century protractors were widely used in mathematics and geometry.
By the twentieth century every maths classroom had a plastic version of the semi-circle protractor divided into one hundred and eighty parts.
These days computer aided programmes are more likely to be used in scaled plans than using a protractor manually.