THE PLATE OF BRASS
Sir Francis Drake's Plate of Brass (the Plate) was discovered in mid-1936 by Beryl W. Shinn on a ridge overlooking San Francisco Bay and the San Quentin Peninsula.
This area was subsequently developed and is now known as Greenbrae. For several months Shinn kept the as yet unidentified object and showed it to friends until one of them suggested that he show it to Dr. Herbert E. Bolton, a past President of the American Historical Association, a Historian of international fame, an expert in deciphering inscriptions and a Professor of History at the University of California (Berkeley). In February 1937, Dr. Bolton examined the item and determined that the old odd looking brass plaque appeared to be Sir Francis Drake's original "Plate of Brass".
On April 6, 1937 Dr. Bolton made a public announcement of the discovery at a well-advertised meeting of the California Historical Society and proudly proclaimed that "One of the world's long-lost historical treasures apparently has been found". The following day both the San Francisco Chronicle and the Oakland Tribune carried full accounts of the meeting with pictures of the Plate.
For $3,500 Shinn sold the artifact to the California Historical Society who in turn presented it to the University of California. The CHS also furnished a sum of money to be used "for such test or tests as to determine the genuineness of the Plate as might seem desirable".
Testing of the Plate was performed by Dr. Colin G. Fink, Head of Electrochemistry, at Columbia University, Dr. E.P. Polushkin, a consulting metallurgical engineer for New York City and Professor George R. Harrison of the Massachusetts Institute of Technology. The examination was conducted using the most advanced scientific tests available and took more than seven months to perform. On September 16, 1938 they submitted their report to the University of California and concluded: "It is our opinion that the brass plate examined by us is the genuine Drake Plate referred to in the book, The World Encompassed by Sir Francis Drake published in 1628". An article containing a photograph of the Plate appeared in an article published in the Christian Science Monitor in 1939.
For decades the Plate was displayed around the world and it was considered by many to be the most famous historical artifact ever discovered in the western United States.
The Missing Set of Tools used to create Drake's "Plate of Brass" was discovered near
"The Treasure Site"
The Tracing Tools
In ancient metalworking terminology, the tools were known as tracers. Highly skilled Spanish metalsmiths used tracers to form the pattern of the metal "bezel" of rings (jewelry). The bezel holds the stone and is considered to be part of the "setting". Sir Francis used these tools as a rough pattern for the vertical lines in the text of the Plate of Brass
Close-up of Guilding on a Tracer
Comparing the style of the letters on the Plate of Brass with the results from rolling the tools onto modeling clay.
The Rod was used to make the horizontal and sharpen the diagonal lines on the Plate of Brass. The Rod's ancient metalworking features were measured by an Engineering company and they match the lengths of the horizontal and diagonal lines that form the inscription of the Plate of Brass. One end of The Rod was used to make the period marks.
The Hammering Plate
After casting, the Plate of Brass was hammered over the Hammering Plate to give it an older and more sophisticated appearance. After hammering, the edges of the Plate were sheared or cut in order to improve the appearance of the finished product.
The Original Rod
The Rod used to fabricate the "Plate of Brass" was cast at Nova Albion. Along the edge of the San Rafael Marsh the "Original Rod" was discovered. The "Original Rod" is approximately the same length as "The Rod" and has the identical edge functions used to make the lines for the Inscription on the Plate of Brass.