The Douglas Combined Protractor & Parallel Rule is a navigation tool used for plotting and measuring courses on charts. The left side is used as a ruler to indicate the course of bearing. Aligning the protractor allows for direct reading of angles from the nearest meridian or parallel. It can also act as a parallel rule for transferring bearings across a chart and assist in calculating departure and difference of latitude between two points. It’s accuracy is noted to half a degree and it was designed by a British naval officer, Captain H. Douglas, R.N., around the early 1900s. It was used during WW2, and possibly during the VERY late stages of WW1 too.

Made out of translucent plastic, and housed in a card slip, it has a small hole in the centre. On the front of the cardboard slip, is a sticker which combines as a type of label, but also, the instructions. There’s also a small tie, for hanging and securing.

The protractor itself is in excellent condition, with all the black markings in perfect order. There are no chips on the outside edge and the cardboard slip is also in excellent condition. The bottom edge is a tiny bit worn, as displayed in the pictures, but overall, it’s in excellent condition. All too often these sort of things end up dog-eared, bent or at the very least stained. This one, has none of this.