Beginning in 1661, boys who aspired to become officers were sent by their families to serve on ships with a "letter of service" from the crown, and were paid at the same rate as midshipmen. The letter instructed the admirals and captains that the bearer was to be shown "such kindness as you shall judge fit for a gentleman, both in accommodating him in your ship and in furthering his improvement". Their official rating was volunteer-per-order, but they were often known as King's letter boys, to distinguish their higher social class from the original midshipman rating.