This is a Negretti & Zambra weather forecast slide rule, patented in 1915.  It is of heavy brass construction and measures 4.75 inches in diameter.  The front has three circular rings.  The user turns the middle ring, using a lever on the back, until the small arrow points to the wind direction for the observed pressure tendency and the season in question.  The user then turns the central disk until the large pointer at the top is lined up with the observed barometric pressure.  The weather forecast then appears in the slot on the bottom.  I'm not sure of the years of manufacture, it doesn't appear in any of my Negretti & Zambra catalogs.

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