​This is a Friez Model 340 anemometer.  It's shown in the 1931 Friez catalog (available on this website), describing it as the new 3-cup US Weather Bureau pattern anemometer.  The USWB started using 3-cup anemometers in 1928.  I suspect this example is newer, perhaps from the 1950s.  Known as the "S Type" anemometer to the USWB, it has 5 inch diameter hemispherical cups.  The wind speed is read in miles and fractions of a mile directly from the dial.

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