The 4cents Thatcher Ferry Bridge stamp is a famous error of Canal Zone. Thatcher Ferry Bridge was a bridge built which crossed the Panama Canal is as famous as the stamp itself.
The stamp originally depicts a silver bridge joining the two continents i.e. North America and South America. However, one pane of fifty stamps was released without the silver ink used to depict the Bridge. This error is likely to have made this issue the most famous Canal Zone stamp.
The stamp features a half of the globe with two continents. At the top, circling the globe there is an inscription “THE THATCHER FERRY BRIDGE INITING CONTINENTS 1962”. A white stripe can also be seen along with an inscription “PANAMA CANAL UNITING THE OCEANS 1914”. The denomination is at the top right corner.
Today, examples of this famous error are still owned by collectors and are valued at many thousands of dollars.
Image Courtesy: https://en.wikipedia.org