86.510.  Definitions. — The following words and phrases as used in sections 86.510 to 86.577, unless a different meaning is plainly required by the context, shall have the following meanings:

  (1)  "Board of police commissioners" shall mean any board of police, board of police commissioners, police commissioners and any other officials, or board now or hereafter authorized by law to employ and manage a permanent police force in said cities;

  (2)  "Pension system" shall mean the police pension system of said cities;

  (3)  "Policeman" or "member of the police department" shall mean any regularly employed officer or employee of the police department of said cities employed and commissioned by the board of police commissioners of the said cities for police duty but shall not include any police commissioner or anyone employed in a clerical or other capacity not involving police duties and not commissioned by the said board as a police officer.  In case of doubt as to whether any person is a policeman within the meaning of sections 86.510 to 86.577, decision of the board of trustees shall be final.