Adam McNaughtan's song "Our Hamlet" (hilarious, if you've not heard it -- summarizes the entire play in about five minutes of singing) has a line with a reference I don't get:

Then a troupe of traveling actors, like Seven-Eighty-Four Arrive to do a special one-night gig in Elsinore...

Is/was 784 an itinerant UK acting group? Or what?

Please enlighten, if you know.