The word "weathervane" is derived from the old English word
"Fane," meaning flag or banner.


As early as 48 B.C., the weathervane was a part of the ancient culture.
  A life-sized replica of the Greek God Triton was placed atop
the Tower of Winds in Athens.  Mankind has been relying on wind changes
and weathervanes to predict weather for centuries.

They were introduced to America by European immigrants to the
New World and for more than 100 years have been the most
popular American Folk Art form.  Some were used as scientific instruments
determining wind directions for farmers as well as the city dweller,
and as location markers for many farms as well as businesses.
Recently, they have become a collectible item.  In the past 50 years,
the "train" weathervane has been considered the most rare
and valuable to collect, the reason being that there were few
train stations in the settling of our early small towns.

The most popular weathervanes are barnyard animals (rooster, cow, horse).
Har-Ber Village displays 4 weathervanes: horse, horse with sulky and driver,
an eagle and an arrow.  As you travel through the Village, be sure to look up
for a view of these incredible pieces of folk art.  They are residing atop
buildings #12, #104 and #110.

Primary criteria in the valuation of weathervanes are
"size," "form," and  "surface."
"Surface" is the most important.  When leaving the factory, they are covered
with gold leaf squares applied to the copper or zinc form.  Exposed to
outside elements, the gold leaf deteriorates and the copper or zinc turns
to a green verdigris color.  This element could actually enhance the beauty
and value of the weathervane if it is in its original state.

In the collectible market, weathervanes will sell for hundreds, thousands
and even millions of dollars if they have a superior surface.

Source for this info is from the
Weathervane History site on the Internet