Section 470. When guards and other employees may be retired

A guard or
  other employee in a state prison or reformatory, or an employee  in  the
  department  of correction, who shall have served a term of employment of
  twenty-five years, which employment, in the case of a guard or  employee
  in  a  state  prison or reformatory, was either wholly in such prison or
  reformatory  or  partly  therein  and  partly  in  another   prison   or
  reformatory or in a state hospital or penitentiary, or which employment,
  in  the  case of an employee of the department of correction, was either
  wholly in such department or the former  prison  department,  or  partly
  therein   and  partly  as  a  guard  or  other  employee  in  a  prison,
  reformatory, hospital or penitentiary, or in one or more  of  them,  and
  which,  in  the  case of any such guard or employee in a state prison or
  reformatory or employee in the department of correction, was  either  in
  one consecutive term or in two or more terms which shall together amount
  to  a total period of employment of twenty-five years, may, if unable to
  perform his regular duties in a manner satisfactory to the  commissioner
  of  correction be retired as hereinafter provided at one-half his annual
  salary for the year immediately preceding such retirement.  An  employee
  who  retires  on  or  after April first, nineteen hundred seventy, shall
  receive an additional pension of two per centum of  his  average  annual
  salary  earned  during  the three years immediately preceding retirement
  for each year of service in excess of  twenty-five;  provided,  however,
  that  the  total  pension provided by the state pursuant to this section
  shall not exceed seventy-five per centum of the  average  annual  salary
  earned during the three years immediately preceding retirement. Any such
  guard  or  employee  who  is  physically or mentally incapacited for the
  performance of duty after a total period of employment of  twenty  years
  shall  be  retired  and paid annually a pension of forty per cent of his
  annual salary for the year immediately preceding such retirement plus an
  additional two per cent for each year of  service  after  twenty  years;
  provided,  however,  that  such  pension  shall  not exceed one-half his
  annual salary for the year immediately preceding such  retirement.  Such
  pension  shall  be  paid  annually as long as such disability continues,
  upon  certification  of  a  board  consisting  of  the  commissioner  of
  correction,  the attorney general and the comptroller. Any such guard or
  employee who shall have reached the age of seventy years, who shall have
  served a term of employment of not less  than  fifteen  years,  may,  if
  unable  to  perform  his  regular duties in a manner satisfactory to the
  commissioner of correction be retired as hereinafter  provided,  and  be
  paid  such  proportion  of  one-half  of  his annual salary for the year
  immediately preceding such retirement, as the  number  of  years  served
  bears  to  the  full  term  of  twenty-five years. Prison or reformatory
  service shall include the service in time of war of honorably discharged
  officers, soldiers, sailors, marines, and army nurses  who  were  actual
  residents  of  the  state  at  the time of their entry into the military
  service of the United States, and the service of members of the national
  guard in the military service of the United States pursuant to  call  of
  the  president for Mexican border service. Such payment shall be payable
  out  of  moneys  appropriated  therefor,  and  shall  not  be   revoked,
  diminished or subject to the claims of creditors. Such guard or employee
  may be retired when such action shall be in the interest of the state in
  the  following  manner:  A  guard  or  employee  of  the  department  of
  correction shall  be  retired  upon  approval  of  the  commissioner  of
  correction  at  the  expiration  of  twenty-five  years of service, upon
  application for such  retirement  to  the  commissioner  of  correction.
  Within  the  meaning  of  this section, an employee of the department of
  correction  means  any  person  employed  under  the   commissioner   of
  correction.