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The ornamental design for an optical refraction testing instrument, substantially as shown. |
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FIG. 1 is a perspective view of an optical refraction testing instrument, showing my new design.
FIG. 2 is a front elevational view thereof.
FIG. 3 is a top plan view thereof.
FIG. 4 is a side elevational view as taken from the left hand side of FIG. 2.
FIG. 5 is a bottom plan view thereof.
FIG. 6 is a rear elevational view thereof.
Copeland, Victor L., Toth, John E.
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| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Apr 04 1975 | Nerthus, Inc. | (assignment on the face of the patent) | / |
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