I've obtained this instrument in 1996 together with the Kelvin Hughes station pointer in my collection. The instrument is used for coastal navigation using a sextant and was invented in 1801 by Joseph Huddart, a U.S. naval captain.¹

This instrument, also referred to as a three-arm protractor, is composed of a circular scale connected to three arms. The centre arm is fixed, while the outer two can be adjusted to an angle previously measured with a sextant.

In coastal navigation the vessel's coordinates can be established by measuring two horizontal angles between three coastal objects. After setting the legs of the station pointer to these angles (adjustment is done with two verniers, see figure 9 and figure 10) it can be laid on a map showing the same objects (see figure 2). With the legs running over the objects on the map, the centre of the instrument will be your position in it.

To mark the acquired position four types of centring pieces were supplied with the instrument (see figure 12): a pencil piece, a cross-hair, a fixed prick and a push prick.

This protractor has Serial Number 7700 (see figure 5 and figure 6), and was manufactured in 1942. Warren-Knight made hundreds of them during WWII. The number 70 on the back of the instrument (according to one of the instrument makers over there for almost 60 years) is probably the number of the instrument from the "Lot" or group of instruments made at one time. The number stamped on the back would help the instrument makers keep track of what parts went with which instrument as they were being made as the parts were all hand fitted due to the accuracy that had to be achieved for these instruments.²

This model protractor is still produced on request by Warren-Knight as Model #WK-24-1175L. The mirrored version (able to close the right hand legs) is manufactured as Model #WK-24-1175R.

The Warren Knight station pointer was once bought by Osiris-Ceso BV in the Netherlands. Although the company sticker that would once have been on the lid is gone now, the other station pointer in the collection also came from that same company and still bears their company sticker.

Osiris-Cesco had started in 1965 as Dredging Investigations, a subdivision of Boskalis, one of the world's leading dredging companies. It was renamed Osiris Survey Projects in 1975 and became Osiris-Cesco in 1978 due to a joint venture with Fugro-Cesco. As the company sticker indicates Osiris-Cesco was a "Survey and Site Investigations" company. In 1988 they became Osiris Seaways Ltd, which I joined in 1989. It then became Osiris BV, and was sold to the French CGG (Compagnie Générale de Géophysique) in 1994. It finally dissolved into Fugro at the end of the 20^th century.

Shortly before I left Osiris in 1996, I was given these two station pointers, which otherwise would have ended up in the skip.