No.: 27,843 Lake lnventor: Assignee: References Cited UNITED STATES PATENTS 1/1936 Terwilliger ..40/132 E Apr. 4, 1972 Primary Examiner-Robert W. Michell Assistant Examiner-Richard Carter Attorney-Kinney, Alexander, Sell, Steldt & Delahunt [5 7] ABSTRACT Contrasting background for display of letters, numbers, or other indicia is provided by using a sheet of louvered material in which thin parallel