This solid state head appears in the Bell Musical Instrument catalogues for 1975 and 1976/77. As it has a Compression control, it may well have been intended more for bass than anything else but there’s no reason why it can’t be used for any instrument. It uses a fairly standard 100 watt power section utilising a pair of 2N4348 transistors. It’s very similar to the 100 watt power amp sections used in earlier amps such as the ER100 although it’s interesting to note that there is no voltage selector on this amp. I also have the 40 watt version of this amp, the GX40, in my collection. I acquired this amp in July 2017 and it was already in very good, working condition. All I needed to do was to clean and polish the tolex, fit a new handle, and replace the old Bulgin mains connector with an IEC connector as  the old Bulgins will not meet modern safety standards.