Orthops Slide Rule

Catalogue Number: 1931
Orthops Slide Rule
Category: Equipment
Sub-Category: Dispensing tool
Year Of Publication/Manufacture: 1930s
Time Period: 1900 to 1939
Place Of Publication/Manufacture: London
Publisher/Manufacturer: Raphael's Ltd
Description Of Item: White plastic rule with metal slide and various scales on both sides. Marked on one side 'ORTHOPS SLIDE RULE RAPHAEL'S LTD LONDON'
Historical Significance: Raphael's Ltd made various rules for the measurement of facial and spectacle frame dimensions (as indeed did many other optical supply companies. (See British Optical Association Museum online catalogue for a number of examples and also the Kett Museum catalogue) . This reflected the desire of early 20th C optometrists and opticians to be as precise as possible in fitting spectacle frames. The British Optical Association Museum has two paper items that give a description of this rule and its use. The material of this rule is probably ivorine, any early plastic made of cellulose nitrate. See Cat No 1940 for instructions for its use and Cat No 1449 for an earlier version. The book L S Sasieni Spectacle fitting and optical dispensing 1950 (Cat nos 776 )2243) has an informative chapter (ch 2) on frame rules and one (ch 5) on devices for face measurements.
How Acquired: Donated by British Optical Association Museum
Date Acquired: July 2011
Condition: Excellent
Location: Archive office. East wall shelves unit 3. Drawer 5

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