Spy-glass.

This optical instrument, monocular was used to see extended objects located at a given distance. It is known that Galileo Galilei was the one who modified a telescope for use in his astronomical observations in 1609, but it is not known with certainty who was the inventor of the instrument.

There are those who attributed his design to the German Hans Lippershey in 1608, others ascribe it to the Dutch in the discovery (three patented in a month in 1608 in The Hague, separately) and there are some who are related to an optical Catalan called Juan Roget, or even with the court of Philip II.

Whatever the case, it is an object very much used for nature-related activities such as bird watching, surveillance or navigation. In the NINETEENTH century, it was essential for the presence of these various instruments onboard all the ships.