The SPECIAL PLANNED COMMUNITY PRESERVATION DISTRICT is a Special Purpose District designated by the letters "PC" in which special regulations set forth in Zoning Resolution Article X, Chapter 3, apply to all districts which are at least 1.5 acres and contain a minimum of three “buildings”, substantially designed and developed as a unit with substantial clustered OPEN SPACE and related “commercial uses” available to all residents of the District under the regulations of the Zoning Resolution prior to December 15, 1961, which was considered to be worthy of such preservation by the City Planning Commission and the Board of Estimate, or its successor, and designated pursuant to Section 103-05. The Special PC District and its regulations supplement or modify those of the districts on which it is superimposed.