EXISTING OFFICE BUILDING, 100' OR MORE IN HT

(1) which on 1/18/1973 is complete or under construction, or (2) for which plans have been filed before 1/18/1973 and construction commenced on or before 1/18/1974, or (3) for which plans are filed on or before 1/18/1974 and construction commenced on or before 1/18/1975 and further provided that all the requirements for such existing office buildings are fully complied with in the course of construction and before completion. An office building 100' or more in height or a building classified in occupancy group E, 100' or more in height: (1) which on 1/18/1973 is complete or under construction, or (2) for which plans have been filed before 1/18/1973 and construction commenced on or before 1/18/1974, or (3) for which plans are filed on or before 1/18/1974 and construction commenced on or before 1/18/1975 and further provided that all the requirements for such existing office buildings are fully complied with in the course of construction and before completion.