(a) For furnishing uniforms and all other official equipment prescribed by Department regulations as necessary and requisite in the performance of duty there is hereby authorized to be appropriated a sum not exceeding $75 per annum for each member of the Metropolitan Police, to be expended subject to rules and regulations to be prescribed by the Mayor of the District of Columbia.
(b) The Chief of Police of the Metropolitan Police force, the Fire Chief of the District of Columbia Fire Department, the Commanding Officer of the United States Secret Service Uniformed Division, and the Commanding Officer of the United States Park Police force are each authorized to provide a clothing allowance, not to exceed $300 in any 1 year, to an officer or member assigned to perform duties in “plainclothes.” Such clothing allowance is not to be treated as part of the officer’s or member’s basic compensation and shall not be used for the purpose of computing his overtime, promotions, or retirement benefits. Such allowance for any officer or member may be discontinued at any time upon written notification by the authorizing official.