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Dalton Dead Reckoning Computer Model G


This is a metal instrument shaped like a rectangular box. On the top, it has a flat metal plate that is affixed to the box below by a hinge along one edge. When flapped down, this plate sits horizontally over the top of the box. On the plate, there is a circular metal disk with a non-linear scale around the rim, labelled in “Minutes” and “Km Minutes”. There is a circular scale on the metal plate around the edge of the disk; this is labelled in “True Alt.” “Miles” and “True A.S.”. On the interior of the disk, there are two arc-shaped holes each with short scales drawn on the disk above or below the arc. These permit conversion from “Air Temp. Centigrade” to “Ind. Height Thousand Feet” and the reverse. Each of the ends of these arcs holes is raised to allow the disk to be rotated around a central pin.

This plate flaps up to reveal the rectangular box-shaped instrument underneath. It consists of a top metal plate with a circular hole in it. This is covered by a plastic window. Visible through the window there is a red grid pattern printed on a paper or fabric sheet. This can be moved up and down along its x-axis by turning a ridged knob on one side of the box. Around the edge of the window on a silver-coloured circular rim there is a scale graduated in degrees, and with cardinal directions indicated. This rim can be rotated by turning a ridged metal handle on one side of the box.

On one edge of this rotating disk, there is an arc-shaped section with a scale along the bottom edge, graduated in units from 0 in the centre to 40 on each side. One side of this is labelled “Drift Port Var. East” and the other “Var. West Drift Strbd”. In the centre of this arc, pointing towards the rotating circle there is an indicator arrow labelled “True Course”.

Attached to one side of the box there is a hollow cylindrical tube. On the underside of the flat top, there are two plastic rods for holding something flat.

Lying loose between the top plate and the rotating circle, but attached by a loop of cotton string, there is a brown card tag, with a reinforced hole punched at one end. The tag is torn in half. The tag is two-sided, and has spaces for information about the instrument and, a space for “remarks”.

On the rear, there are four round holes in the backplate.

Accession Number: 2019.ast.176

Alternative Name:

Primary Materials:

Metal: Iron Alloy, Metal: Aluminum, Card, Textile (Grid).


Engraved and enamelled next to the grid window: “DALTON DEAD RECKONING COMPUTER

Printed/written on the paper label: “SERVICEABLE
PT. NO. 48
DESCRIPTION Computers Navigation
300M 9-45(5090)
H.Q. 885 E-33”

On the rear: “REMARKS
R.V. NO.

There are a pair of symbols written inside the lid plate.

On the rear: “X.Y. 3498”

Dimensions (cm): Height = 3.5, Width = 16, Length = 16.


The Dalton Dead Reckoning Computer is a mechanical calculator designed to aid with flight planning, including (according to the Wikipedia page on the similar <a href=””>E6B</a>) “fuel burn, wind correction, time en route, and other items.”


Good: The instrument’s surface shows significant evidence of use in the form of marks and scratches on the top and bottom of the box, and the paint has been chipped off the corners and worn off the knob edges. The top surface of the metal lid is corroded across its surface.

The hinges of the lid are in good condition. The continuous rotating grid inside the instrument is broken and no longer rotates. The plastic window covering it is slightly yellowed and scratched on the surface. The cardboard label is bent but in good condition.

Associated Instruments:


Stanley Manufacturing Co. Limited, Toronto, Canada

Date of Manufacture: c. 1939-1942


This artifact was purchased as surplus following WWII and may have been used for teaching at the Department for the Astronomy & Astrophysics or at the David Dunlap Observatory, possibly as a slide rule. If the former, it was probably moved at some point to the Observatory for storage. The sphere was kept at the David Dunlap Observatory until 2009. Upon the sale of the Observatory, it was moved to the University of Toronto’s Department of Astronomy & Astrophysics at the St George Campus. In 2017 it was moved to a new storage location in McLennan Physical Laboratories.

Additional Information and References:

Historical Notes: