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Map measure of the month: The Oldbury Optical Distameter

“For measuring on maps, roads, railways, rivers, canals etc.”

The Automatic Distameter
Close up of face
Oldbury Optical Distameter
Olbury Optical Distameter
Oldbury Optical Distameter
Reverse of instrument case
Reverse of instrument case is plain, with no markings of any description

The Oldbury Optical Distameter is an ‘English’ made map measure that dates from the 1960s. It is pretty typical of the style of long-handled map measure also being manufactured in other countries such as France, Germany and Switzerland.

It is possible that this measure was actually manufactured by French manufacturer Henri Chatelain, then rebranded, as Oldbury did previously retail HC measures.

The distameter is 117mm long of which 68mm is the hexagonal handle. The instrument case measures 36mm across with a 28mm face. The dished glass cover gives a slight magnifying effect to the paper dial. The measure is 7mm thick at its most extreme point at the centre of domed glass face. This is no heavyweight measure, weighing just 40 grams. One revolution of the dial by the blued needle measures exactly four inches. Each inch on the paper face is divided into 16ths.

Conversion table supplied with the Distameter
Conversion table supplied with the Distameter

A conversion chart, from 1/16ths of an inch to yards, is provided both on a small piece of card in the box, and on one side of the card lid to the box. This also informs us that one inch measured and indicated on the dial translates as one mile. So a full turn of the dial indicates four miles measured at a scale of one inch to the mile. With each turn of the dial, a small counter visible through the dial face is moved on by one digit. This totaliser records 0-9, then returns to 0. So a possible total of 40 inches, or 40 miles.

Front of box
Side 1
Back of box
Side 2

Three tiny screws hold the front face in place. Other than these, all internal workings revolve around small brass pivot pins. The internal workings of this measure are not quite as smooth in operation as some totaliser measures made by other companies. As the measure is being tracked along a line on a map and the needle rotates around the dial, when it reaches the number three there is a distinct internal ‘catch’ in the gearing, presumably where the internal action is engaging the number rotating mechanism. It passes instantly and does not interfere with the effectiveness of the measure when in use.

As usual, it can be difficult to tie these instruments down to a particular date period however, along with the style of illustration on the card box, another example of the measure points us toward the 1960s. The Oldbury Distameter would have been used by a wide range of users for a wide range of purposes. The additional example of the measure shown here, from the collection held by The Postal Museum, has the letters ‘G.P.O.’ stamped on the case. These stand for ‘General Post Office’. This was the identity of the British state-owned telecommunications and postal service. This obviously points at a use prior to that organisation becoming a corporation in 1969, from when their initials were simply- ‘P.O.’. No doubt this particular measure was an official issue and was used for measuring the length of postal deliveries, or routes to be taken by bicycles and other postal vehicles. 

The Postal Museum- Map Measure
Distameter from The Postal Museum collection
The Oldbury Optical Distamter came in a card box with slip lid and a small conversion table
The Oldbury Optical Distameter came supplied in a card box with slip lid together with a small conversion table

Oldbury Optical Co. Ltd., the maker, or at least retailer, of the Distameter, were manufacturers and suppliers of optical equipment and instruments and were based in London, U.K. Under the Companies Act they were removed from the Department of Trade Register of Companies in June 1972, the company being dissolved at that time.

Three Points of the Compass has looked at a few more Map Measurers in detail. Links to these can be found here.

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