I have been closely following the market for Audio Guild amps for years, and own five of them. There are certainly more than ten or a "few dozen" bass combo amps produced by Audio Guild. They are rare, but not that rare. Some of the Audio Guild bass amps were branded "Versatone," others were "Bonham." They are essentially the same bass amp, with different graphics.
People often conflate the bass amp version (1 channel with only volume, treble, bass, pan control knobs, and two output transformers) with the more common accordion/guitar versions branded, "Versatone," "Bonham," "Universal," "Lyric," "Titano" (2 channels with eq controls, reverb and tremolo; either dual or single output transformers). The cabinets for the bass amps and guitar amps look the same, so the easiest way to distinguish them is to count the number of control knobs, i.e., the bass amp has only four.
You can play bass guitar through the guitar/accordion amps that use the same 7591A power tubes, dual output transformers and speakers as the bass amp, and get a nice sound. (Before she used Versatone bass amps, Carol Kaye says she used Fender Super Reverb and Concert guitar amps for bass). But, IMHO, these guitar/accordion amps do not sound the same for bass guitar as the simpler bass amp version, particularly when overdriven. The bass amps are, indeed, special.