What did the FA phone exchange stand for?

While enjoying the views along Edgecombe Avenue in Upper Manhattan, I spotted this rusted sign containing an old two-letter phone exchange, once ubiquitous in New York until they were phased out in the 1960s.

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The FA exchange is a mystery. Gun Hill is a road in the Bronx, and the Gun Hill Fence Company, founded in 1959, still operates in the Bronx, now in a site on Boston Road.

Fordham is my best (but probably not accurate) guess. These old two-letter telephone exchanges are fun to find in hidden pockets of New York City.