UPDATE: There has been some interest in the Barclay St. sign also shown in this photo. This is a standard street sign for that area. Here is some info about the Twin Towers depicted on the sign:
The World Trade Center is remembered in Downtown Alliance street signage. The lower Manhattan business and tourism promotional organization, in the early 2000s, installed black and white street signage designed by Cooper Robertson and Partners, as well as new lightposts and area maps.