NYC Zoning Handbook: Appendix E
Commercial Districts: Permitted Uses
 In all districts except C7, uses must be located within completely
enclosed buildings. Open store fronts and store windows are allowed,
however, in C2, C3, C4, C6-1 through C6-4, C6-6, and C8 districts.
In certain C5 and C6 districts in Manhattan (Community Districts 1 to
6), all pre-existing lawful Use Group 17B or 17E uses, when located in
pre-1961 buildings shall be considered conforming. In C6-2M or C6-4M
districts, any use of Use Group 17B or 17E shall be permitted in a
pre-1961 building by right.
In C6-1G or C6-2G districts, residential
uses are allowed by special permit of the City Planning Commission in
certain pre-existing non-residential buildings.