c1965 Bird Big 15, courtesy of Nick Heywood, Liverpool, England
This model seems to be a development of the 15 watt Golden Eagle amp. However it was fitted with a single 12" speaker instead of the Golden's triple elliptical units. It was advertised as "specifically designed to handle peak loads without distortion". Presumably the 12" speaker was an improvement in this respect. The Golden Eagle certainly produces a rather individual overdriven tone very easily !
Three input jack-sockets were provided as opposed to the Golden Eagle's two. Other than that, we can only assume that it was very similar internally to the Golden Eagle 2/15.
The Bird Big 15 scanned from the Bell Musical Instrument catalogue of September 1964.