The following is from
http://www.smalldollars.com/dollar/page33.html
"For business strikes, the edge lettering is being applied in a seperate process
after the obverse and reverse are struck. The struck coins are run through the
edge lettering machine at a high speed without reguard to whether they are
facing obverse up or reverse up. Therefore, coins are being struck with "edge
lettering right-side-up" and "edge lettering upside-down" in relation to the
obverse of the coin (SEE PHOTOS BELOW). "Upside down" lettering IS
NOT AN ERROR. However, it is a nice variation to collect one of
each type if one is inclined to do so.
The edge lettering on proof coins is applied by a
different process than on business strikes. It is applied when the coin is
struck."
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