Holy Smokes! That is a pretty impressive cast of endorsers...they definitely had some awesome sauce in their stuff back then.
They were one of the largest players in the bass amplification market. They also made small runs of extremely high quality basses that are very much sought after still, today. In the 1990s, they also expanded into acoustic guitar amps, dominating that field for years, and they also produced several excellent lines of guitar amplifiers, some of which were sold as Gibson amps after Gibson bought Trace Elliot from Kaman.