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.