The minimum service required to qualify an applicant for an endorsement as mate of Great Lakes and inland self-propelled vessels of less than 500 GRT is 2 years of total service in the deck department of self-propelled vessels. One year of the required service must have been on vessels of 50 GRT or more. Three months of the required service must have been while performing bridge watchkeeping duties under the supervision of the master or a qualified officer on vessels of 50 GRT or more.