First seen used in August 1980 during the "Is There Anybody Out There?" Tour. It was seen on Phil Taylor's sketch on the arrangement of David Gilmour's live rig in Vernon Fitch’s “Comfortably Numb: A History of “The Wall” Pink Floyd 1978-1981”. It was used as a "FUZZ" effect with a dedicated dummy load with a remote footswitch. The switch and amp can been seen in his "About Face" Tour Rig in 1984 and was used right up until the 1989 Venice Tour. These MESA/BOOGIE Mark I heads were made-to-order and can be customized with EQ or Reverb. In David's case, his unit was a 60W rather than the 100W (the dummy load is rated up to 80W as seen), along with the a multi-voltage selector (his unit was ran at 110V as seen in Phil Taylor's sketch).

Santana's guitar tech pointed out that Carlos Santana uses a Mesa Boogie Mark I for his work.

Used on Dinosaur, as stated in this August 24, 2011 interview with Kit Rae.

KR: What amps were you using in the early days with Dinosaur? Like the first three albums?

JM: The first album, I used a very early 60 watt Mark I Boogie that a guy had at the studio where we recorded. That sounded pretty cool. I used the Marshall a little bit, but mostly the Boogie on that album. Then the other albums, for Bug and You’re Living All Over Me, I used a 50 watt Marshall head. And then after Bug, I kind of got into (Marhsall) Super Leads more. You know, as I got more money I discovered things like Plexis.

"While on Weezer's Northern California tour in August '92, Rivers bought a curious Mesa/Boogie amplifier (pictured inside the Blue album cover on the left side) at the Berkeley Guitar Center. I have never ever seen an amp exactly like this one since. It was a very early issue Mesa/Boogie, from approximately 1977 or 1978, and its face plate said "Mesa Engineering", which predates the addition of "Boogie" to Mesa/Boogie's name. It was a 60-watt head which apparently didn't even have a model number (I remember looking for one several times).

It sounded incredible, and its real bonus was still sounding rich and thick even at low volume, making it ideal for recording demos late at night in the Garage. Sadly, while on tour in '96 (by this time as a backup amp), the Boogie suffered a near fatal blow from an unknown source during shipping. At some point during the tour, the amp was fired up to check it, and it sounded terrible. It was supposed to have been taken in for repairs, but apparently was lost somewhere, either at Weezer's storage facility in Los Angeles or later, when Rivers was living in Boston. No one seems to remember where they saw it last, and it is gone. Several fans have written in with info on this amp, but most identify it from the reissues. I have checked the reissues but none are exactly the same. However, several people wrote in with the explanation that this was the 60-watt version of the Mark I head. The reason that the amp had no name on it is that it was not named until Mesa/Boogie issued their next amp, the Mark II. A reissue version of the Mark I is available right now from Mesa/Boogie in a 100 watt head or combo form with a switch to reduce the power to 60 watts, and it is that edition that some people were confusing the "vintage" amp with. Patrick Wilson today owns a Mark I reissue in fact, and can confirm that the old one had some pull out knobs that produced amazing sounds that the current reissues do not produce. It's entirely possible that the pull-out knobs were a custom job..." - Karl Koch, weezer.com

Lindsey switch to mesa boogie in October 1977. He used the Mark 1s From 1977-1995

Listed on the official website of John Scofield

Brian used the Mesa Boogie Mark 1 amp he borrowed from Rivers through out summer of 1994, though he changed the amp 2 times before he got his JMP Plexi but this amp was used for the most of time. It also had few stickers, some gold sticker + custom Weezer sticker. He might also used it at Undone B-Side sessions in June of 1994.

Laner's Tumblr page contains several shots that feature his Mark I combo.

As mentioned on Stuermer's official website.

Neste video do canal Custom Shop Brasil o guitarrista apresenta seu "mesa boogie Mark I 60w" utilizado em um show da nação zumbi em 2018-2019

Obs: o amp na foto da plataforma é diferente do amp mostrado no video, mas trata-se de um mesa Mark I nos dois casos.

In an interview with Australian Musician Magazine, Phil Knight discusses using the Mesa/Boogie Mark I guitar amplifier head.