§ 64. Licenses. Every person employed as a master, pilot, engineer or joint pilot and engineer, on board of a public vessel, shall be examined by the inspector as to his qualifications, and if the inspector is satisfied therewith, he shall grant him a license for the term of one year. In a proper case, the license may permit and specify that the master may act as pilot, and in case of small vessels may also act as joint pilot and engineer. The license shall be framed under glass and posted in some conspicuous place on the vessel on which he may act, provided that on vessels of less than ten tons, the license must be carried but need not be posted. Whoever acts as master, pilot, engineer, or joint pilot and engineer, without having first received such license, except as in this article otherwise specified, shall be guilty of a misdemeanor. An applicant for license as master, pilot, or engineer, must be at least twenty-one years of age. An applicant for a license as joint pilot and engineer must be at least eighteen years of age.