The Chief Administrative Officer of the House of Representatives is on and after July 2, 1954, authorized to pay, from the applicable accounts of the House of Representatives, a gratuity to the widow, widower, or heirs-at-law, of each deceased employee of the House an amount equal to one month's salary for each year or part of year of the first six years service of such employee plus one-half of one month's salary for each year or part of year of such service in excess of six years to and including the eighteenth year of such service. Service computed hereunder shall include all Federal civilian employment, and military service where such service interrupted Federal civilian employment.