By 1961 or 1962 Don Bonham had ended his relationship with Magnatone other than a licensing agreement for his vibrato.
Bonham incorporated the Audio Guild Corporation (AGC) in 1966.
In addition to amps branded "Audio Guild", AGC made OEM amps for other retailers including the aforementioned Versatone, Universal, and Panaramic & Titano. Ernest Deffner, a partner in Pancordion Accordion Co., bought Titano Accordion Co. in 1965. Following the acquisition, both Titano and Pancordion switch OEM sourcing from Estey to AGC.
AGC also manufactured amplifiers for Versatone.
There were several circuits made by AGC, all of them well engineered. Most, if not all, centered around 7591A power tubes. Reverb and vibrato effects were used on guitar amps. Some models had stereo output transformers with four 7591A power tubes, although unlike some of the Magnatone stereo amps, the AGC's were engineered to send different parts of the signal to one amp, and other parts to the other (high frequencies to a 10" speaker in an open back chamber of the cabinet, and low frequencies to a 12" speaker in a closed back chamber).
The cabinet designs were unique. AGC obviously wasn't in the business of cloning Fenders, Magnatone or Ampeg designs. Some cabinets had had three chambers, one for the amp, one for one speaker in an "open back" design, and one speaker in a sealed back chamber. Single speaker AGC combo's were made as sealed chambered cabinets. All of the AGC's I've seen used Utah ceramic speakers, but other speakers might have been used as well.