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This is a historical event. (one that happened in the past)
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This is a historic event. (one that is important in history, e.g., the Moon landing)

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He was a historical scholar. (A scholar who studied history)
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He was a historic scholar. (A scholar who was important in history, e.g., Homer)

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The bones were of historical significance. (significant from a perspective of history, i.e., possibly worthless but important to study history)
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The bones were of historic significance. (very significant, i.e., important in history)
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