seven segment display history

[Jules Richardson]

Does anyone know when seven segment displays first appeared on the scene? 
Presumably the first ones were VF, and LED came later?

(I was just looking at a museum's mock-up of the Apollo mission control 
console, and the fake readout is made to look like a 7-seg display; I'm just 
surprised that the digital readouts weren't all Nixie-based back then)

cheers

Jules