Pub. L. 85-584, tit. III, sec. 304

Sec. 304. Any officer or member who is promoted or transferred to a higher class shall receive basic compensation at the lowest rate of such higher class which exceeds his existing rate of compensation by not less than one step increase of the class from which he is promoted or transferred. If the existing rate of compensation of an officer or member is above the maximum longevity step increase in the class from which he is promoted or transferred and there is no rate in the higher class to which he is promoted or transferred, which is at least one step increase above his existing rate, such officer or member shall receive the maximum longevity rate of such higher class or his existing rate, whichever is greater. Any officer or member in any class who is assigned or transferred to any Sub-Class within the same Class shall be placed in the same service or longevity step in such Sub-Class as that which he was in immediately prior to being so assigned or transferred.