I found this insulator over 30 years ago, buried in an old railroad trestle close to the joining of the rails at the Golden Spike site at Promontory Utah. We are having a hard time finding it listed anywhere. Can anyone help us? It has 3 patent dates on the top: March 20 1877, January 25 1870 and February 22 1870. It is a Brookfield, with a number 33 or 55, and FULTON ST NY.