“Policeman” as used in this article includes sheriffs, undersheriffs, deputy sheriffs and any other employee of a county in a position designated as a policeman’s position by the board; provided, any such position named herein or as may be designated by the board, is not contrary to any definition, ruling or regulation issued by the federal agency relating to the term “policeman” for the purposes of Section 218(d)(5)(A) of the Social Security Act.