Catalogue Number: 3776
AO Additive Effective Power Phoroptor
Sub-Category: Refractor Phoropter Phorometer
Corporation: American Optical Co
Year Of Publication/Manufacture: c1934
Time Period: 1900 to 1939
Place Of Publication/Manufacture: USA
Publisher/Manufacturer: American Optical Co
Description Of Item: Black enamelled instrument (phoropter or refractor head) with fitting to mount on an arm of an instrument stand. Each side has inbuilt options of pinhole, plus and minus 0.12DS, red filter, prisms of 6 PD vertically, 10 PD BI, 15 PD BO and an occluder. Each side also has externally mounted clear Maddox rods and variable (Risley) prisms. Plaque on front reads 'AO ADDITIVE EFFECTIVE POWER PHOROPTER/ MADE IN U.S.A./UNDER ONE OR MORE OF U.S. PATENTS Nos 1,409,680/ 1,423,091/ 1,455,457/ 1,483,786/ 1,611,167/ 1,794,571/ 1,887,049/ AMERICAN OPTICAL COMPANY/ U.S.A.' Also black cotton storage bag. Size: 260mm W x 270 mm H x 70 mm D.
Historical Significance: The last of the listed US patent numbers, 1,887,049 , was granted on November 8 1932.
How Acquired: Donated by William Law Optometrist
Date Acquired: October 2019
Condition: Very good
Location: Archive room. West wall. Unit 1 Drawer 4