The New Optrex Datum Rule
 Catalogue Number: 1909 The New Optrex Datum Rule Category: Equipment Sub-Category: Dispensing tool Time Period: 1900 to 1939 Place Of Publication/Manufacture: Glasgow Publisher/Manufacturer: John Baird and Sons Description Of Item: Pantograph rule for measuring various parameters of spectacle frames and for marking up spectacle lenses prior to cutting and edging a lens so that the optical centres of pairs of lenses are at the same height with respect to the datum line of the frame, and when mounted in the frame, are separated by the inter-pupillary distance of the patients eyes. It also has provision for measuring facial characteristics such as nose width and inter-pupillary distance. Cream plastic. Marked with the name and address of the inventor and supplier 'John Baird and Sons Opticians 70 Mitchell Street Glasgow', Patent No 36/012/30 Historical Significance: This item was advertised by John Baird and Sons in the Optician journal 10 Feb 1939. An advertisement for John Baird and Sons describes them as wholesale and manufacturing optician selling telescopes, binoculars and camera as well as spectacle frames and ophthalmic instruments. 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: Good Location: Archive room. West wall. Unit 2 Overhead display |