Advertecture: Is This Billboard On East 79th Legit?

Just asking. This billboard is found on the southeast corner of 79th and Lexington Avenue. Given that the building is only 2 stories (in the tradition of a Lexington Avenue "taxpayer"), you'd have to guess that at least in terms of height, it would be as-of-right, but can you really just throw a 20' high billboard on top of a building like that in a residential area? If anyone knows, please chime in. To me, it looks out of place.