Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Proving Ring Patent
Whittemore and Petrenko submitted a patent for their proving ring, number 1648375, to the United States Patent Office on September 14, 1926. The patent was granted on November 8, 1927. The drawings shown below were part of the original submission.
Created September 11, 2009, Updated November 25, 2019