Section 309. Non-duplication

No compensation under the provisions of this
  article shall be payable to  any  civil  defense  volunteer  or  to  the
  dependents  of  a deceased civil defense volunteer otherwise entitled to
  receive workers' compensation under the provisions of this chapter or of
  any  other  law,  or  volunteer  firefighters'  benefits  or   volunteer
  ambulance  workers'  benefits  under  the  provisions  of  the volunteer
  firefighters' benefit law or the volunteer  ambulance  workers'  benefit
  law  or  of any other law, or if the disabled civil defense volunteer or
  the dependents of a deceased civil defense  volunteer  are  entitled  to
  receive benefits under the disability benefits law or similar statute of
  any  state or under any disability or retirement or insurance program of
  an employer who has  contributed  to  the  cost  thereof  or  under  any
  provision  of  benefits  by or under laws of the federal government or a
  state or political subdivision thereof, except only as herein  provided.
  Compensation  payable  under this article shall in such event, or any of
  them,  be  reduced  to  an  amount  which,  together  with  such   other
  compensation  or  benefits,  shall not exceed in aggregate the amount of
  compensation to which the claimant, or his dependents, would be entitled
  under this article but for such other provision.