In a user-uploaded photo, Rob Grange is seen playing an Alembic Series I Bass.

Andy West owned a custom Alembic Series I Bass with two XLR outputs, as evidenced by a user-uploaded photo on Jasobrecht. He sold it in the 1980s due to financial constraints.

Mentioned in this March 1, 2019 al.com interview.

A vintage photo of Muscle Shoals Rhythm Section bassist David Hood with his Alembic bass. (Courtesy of Dick Cooper)

(...) Later, he acquired an Alembic bass and played that instrument on many of his recording sessions after 1976. "The guys in San Francisco that equipped the Grateful Dead made they [sic] Alembic instruments," Hood says. "I've still got mine. It's got a double-octave neck though and with arthritis in my wrists and shoulders I rarely play it, because it's not really comfortable to play. But it's a great sounding instrument."

This May 17, 2013 Bass Player interview specifies that Hood used the bass from 1976 to 1988.

From 1976 to 1988, he played an Alembic; he also occasionally plays a Kubicki Factor and a 1957 Fender Precision. (Hood’s Jazz Bass was stolen during the Traffic era.) He uses flatwound strings on the Lakland Osborn and the Precision, and roundwounds on the rest. For amplification, he favors a Gallien-Krueger head driving two Ampeg cabinets, each of which has two 12" speakers.

In this February 20, 2014 No Treble interview, Hood discusses his initial switch to the Alembic.

My first bass was a ’61 Fender Jazz. It took a long time, but I eventually got a really good sound with it. I worked with that bass for over 10 years so I knew how to make it sound right and I measured all other basses against that one. That bass got stolen on one of the Traffic tours in ’73 so I immediately went out and got two other Jazz basses. Then I got an Alembic and was able to get a really good sound with that one. People would come in to the studio and say, “Gosh, I thought you played a Fender. What’s that thing?” But it got a great sound, and as always, I was playing and working for the sound that came out of the speakers.

The "Bass FAQ" page of Hood's official website mentions that the '76 Alembic is "[a] veteran of 1,000 recordings, still a great sounding bass."

Here's Rodney playing an Alembic Series I with Funkadelic.

Sabo Romo uses the Alembic Series I Bass, as evidenced by an image of him playing the instrument and a video where he is seen using this bass (youtu.be/o8xaX4oQyxI).

In this youtube video at 22:55 Dan Horne talks about his bass

From 0:56 to 1:06 you can see him playing