Section 262. Alteration of uncompleted buildings

The provisions of this
  chapter relating to multiple dwellings erected after  April  eighteenth,
  nineteen  hundred twenty-nine, shall not apply to any fireproof building
  structurally enclosed but uncompleted on April first,  nineteen  hundred
  forty-five,  conforming  to  the  provisions  of the local zoning law or
  resolution applicable to an apartment hotel, in effect at  the  time  of
  the  approval  of  the original plans filed for the construction of such
  building, and which building shall thereafter be altered  and  completed
  as  a class A multiple dwelling, in accordance with plans and amendments
  thereto approved by the department. Such building,  if  so  altered  and
  completed  on or before July first, nineteen hundred forty-eight, may be
  lawfully occupied thereafter as  a  class  A  multiple  dwelling  if  it
  conforms  with  the  provisions  of  section  twenty-five  applicable to
  fireproof class A multiple  dwellings  occupied  as  such  before  April
  eighteenth, nineteen hundred twenty-nine.