first-class vs first-rate

first-class

first-rate

noun

A first-rate ship of the line.

adj

Of a Royal Navy ship of the line in the Napoleonic Era: having at least 100 guns across three gun decks, a complement of 850–875, and weighing approximately 2,500 tons burthen.
Superb, exceptional; of the best sort; very high quality.

How often have the words first-class and first-rate occurred in a corpus of books? (source: Google Ngram Viewer )