Graph of unknown significance

Plot of pen deflection vs. [interference] fringe number. May be the result of an optical test, a measurement made with the coelostat, or something else. P0657 and P0658 are duplicates. n/a. Extent: 1 photograph. Condition of original material: Stable. Author(s)/Creator(s): English. Scribe(s): Latin. Publisher(s): Left-to-Right. Editor(s): Unrestricted. Volume number: N/a. Original institution reference: PB15_P0658.