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The comparator as it appears in the 1889 Catalogue des Appareils D'Acoustique Construits par Rudolph Koenig. |
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The optics are missing. |
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. |
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The comparator as it appears in the 1889 Catalogue des Appareils D'Acoustique Construits par Rudolph Koenig. |
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The optics are missing. |
|
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