Third-rate

In the rating system of the Royal Navy, a third rate was a ship of the line which from the 1720s mounted between 64 and 80 guns, typically built with two gun decks (thus the related term two-decker).

When the rating system was first established in the 1620s, the third rate was defined as those ships having at least 200 but not more than 300 men; previous to this, the type had been classified as "middling ships".

This designation became especially common because it included the seventy-four gun ship, which eventually came to be the most popular size of large ship for navies of several different nations.

It was an easier ship to handle than a first- or second-rate ship, but still possessed enough firepower to potentially destroy any single opponent other than a three-decker.

By the end of the 18th century, ships of the line were usually categorized directly by their number of guns, the numbers even being used as the name of the class, as in "a squadron of three 74s", but officially the rating system continued until the end of the Age of Sail, only undergoing a modification in 1817.

HMS Buckingham , a third-rater, on the stocks before its 1751 launch .
A model of a third-rate ship of the line of the Navy of the Order of Saint John from the late 18th century.
A painting of HMS Melville (1817) , a British third-rate