Probably acquired for use in Telegraphy courses run at the Ballarat SChool of Mines between 1875 and 1893.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
This relay was made by the firm of Charles T. and John N. Chester, two brothers who successfully partnered in New York City. Charles (1826-1880) founded the firm and provided the expert telegraphy knowledge while John (1820-1871) kept the books and managed the business operations.(http://americanhistory.si.edu/collections/search/object/nmah_706518, accessed 25/01/2018)
Electromagnetic relay device used in telegraphy. The working parts mounted on a brass plate, attached to a wood base. Equipped with four terminal posts. Adjustable contactor mechanism.
This electromagnetic Relay Device was used in Telegraphy at the Ballarat School of Mines. After a special meeting of the Ballarat SChool of Mines Council in 1874, a decision was made to offer instruction in Telegraphy, a subject not directly related to mining. Telegraphy was taught by W.P. Bechervaise, postmaster at Ballarat. On 07 October 1874 the Ballarat Courier correspondent reprted on Telegraphic training: "... these classes ... are a snare and a delusion, as there is scarcely the remotest chance of obtaining employment when the examination has been passed."