Borrowed to use with Curtis Knight and the Squires for two weeks in May 1966, as is visible in this photo of Hendrix found on the "Jimi Hendrix Big Muff" page of Big Muff scholar Kit Rae's website.

Shown above - Jimmy James playing with Curtis Knight and the Squires at the Cheetah Club, New York City 1966. Note the Maestro Fuzztone pedal on the floor in front of the Fender Twin amp

Given that the FZ-1B was not released until 1968, the unit would be either the FZ-1 (the original) or the FZ-1A (released in 1965). The latter two can be told apart by the word "Amplifier" that is only above the output jack of the FZ-1A. Upon further scrutiny of the photo, Hendrix's stombox lacks the word, making it an original FZ-1. Other sources are as follows:

Mike Bloomfield

Guitar Player, September 1975, "Hendrix Remembered" [Corroborative Sources here and here]

The first time I saw Jimi play he was Jimmy James with the Blue Flames. I was performing with Paul Butterfield, and I was the hot shot guitarist on the block—I thought I was it. I'd never heard of Hendrix. Then someone said, "You got to see the guitar player with John Hammond." I was at the Cafe Au Go Go and he was at the Nite Owl or the Cafe Wha? I went right across the street and saw him. Hendrix knew who I was, and that day, in front of my eyes, he burned me to death. I didn't even get my guitar out. H bombs were going off, guided missiles were flying—I can't tell you the sounds he was getting out of his instrument. He was getting every sound I was ever to hear him get right there in that room with a Stratocaster, a Twin (amplifier), a Maestro fuzz, and that was all—he was doing it mainly through extreme volume. How he did this, I wish I understood. He just got right up in my face with that axe, and I didn't even want to pick up a guitar for the next year.

Interview with Ed Ward, excerpted in Michael Bloomfield: The Rise and Fall of an American Guitar Hero (1983, revised 2016) by Ed Ward and Crosstown Traffic: Jimi Hendrix & The Post-War Rock 'N' Roll Revolution (1989) by Charles Shaar Murray

In July 1966 the Butterfield Band was performing at the Cafe au Go Go in New York City when Michael Bloomfield first saw Jimi Hendrix play. “The first time I saw him was when he was Jimmy James, and he was with the Blue Flames at the Cafe Wha? in New York,” Bloomfield told me. “I was playing across the street and I was the local hot guitar player on the street with the Butter Band, and he was just across the street, unknown. I went over there one night, and man, he wouldn’t even shake hands. I mean, he knew how bad he was. He got up there. He had a Twin; he had a Strat, the first fuzztone that ever came out, and there were jets taking off. There were nuclear explosions and buildings collapsing! I never heard anything like it in my life. And it was an off night for him, too. I was sitting right in the front row and he was doing it right to me, like a machine gun. ‘You like this, man?’ B-bb-bbb-room! He was just mowing me down. Oh! Talk about burning!"

Quote in Guitar King: Michael Bloomfield's Life in the Blues (2019) by David Dann

A few blocks from the Cafe Au Go Go, down Bleecker Street and around the corner on McDougal, there was a basement coffeehouse called the Café Wha? Opened in 1959, the club featured a variety of entertainment throughout the daytime and evening hours. Its casual booking policy gave stage time to amateurs and accomplished performers alike, and the fare usually included an odd assortment of comedians, ventriloquists, folk singers, poets, and anyone with a modicum of talent and a desire to perform.

Since June, one of the regular evening acts was a scruffy rock-and-blues quartet fronted by a slight and soft-spoken twenty three-year-old black guitarist who called himself Jimmy James. Folksinger Richie Havens had gotten him the gig, and James was playing multiple nightly sets of rock ’n’ roll covers, pop tunes, and blues for whatever basket money the band could make. What set him apart from other performers at the café was his flamboyant stage presence—and his entirely unique sound on electric guitar. It wasn’t long before word spread that there was a band at the Café Wha? worth checking out.

"I was performing with Paul Butterfield, and I was the hotshot guitarist on the block—I thought I was it," Michael Bloomfield recalled. A friend told him he had to go see the new guitar player working over on McDougal Street. "I went right across the street and saw him . . . and that day, in front of my eyes, he burned me to death. I didn’t even get my guitar out." Michael learned that this formidable guitarist’s real name was Jimmy Hendrix and that he was from Seattle. He looked vaguely familiar, and Bloomfield soon remembered him.

"I had seen him before and not paid any attention to him,” he said. “I’d seen him play with Little Richard and the Isley Brothers." Hendrix had been a sideman for the legendary rock ’n’ roll singer in 1965, and he had briefly toured with the Isleys, but now he was on his own, playing six nights a week at the Café Wha? and tearing up the house. “He had a band called Jimmy James and the Blue Flames. They were obviously just pick-up musicians he had gotten to just learn a few tunes so he could do what he wanted."

From the stage, Hendrix immediately recognized the star of the Paul Butterfield Blues Band. With Bloomfield’s extravagant personality and his equally extravagant swarm of bushy hair, he was hard to miss. Jimmy James decided he would make an impression on the Chicagoan.

“I walked in there and I sat down with a friend of mine, another guitar player" said Bloomfield.

And Jimmy Hendrix watched me sit down—and I remember what he was playing, a Stratocaster, and he had a Twin Reverb amp, a Gibson Maestro Fuzztone, and he had a wah-wah pedal—and he got every sound on those that I was to hear on all his subsequent records . . .

Bombs exploded! Airplanes took off! Buildings collapsed! It was a holocaust! Plus, you know, endless amounts of incredible playing. He just did it with a little half-assed grin on his face. I was sitting in the front row and I was just blown away. It was no contest.

Michael described how Hendrix spent the first part of the set "just making these unbelievable sounds and noises." Using feedback, sustain, wah-wah effects, and distortion, Jimmy created an aural collage of electronic moods. "Then he started playing music," Bloomfield said, laughing. The guitarist’s mastery of amplified sound deeply impressed Michael, but he wondered if Hendrix could do anything else.

"I said, well, he can make all these sounds but, OK, can he really play?" Bloomfield said. "Then I heard him play, and he could play better than he could make sounds!"

(...) "He got right in my face with that ax, and I didn’t want to pick up a guitar for the next year," Bloomfield opined.

Custom Boards, "A detailed look at Jimi Hendrix' pedals and signal chain" (April 23, 2018)

Jimi got his first taste of fuzz in New York in May 1966. He was playing in Curtis Knight’s band, and managed to borrow a Maestro Fuzz Tone pedal off an acquaintance for two weeks. He experimented with fuzz-induced feedback, which didn’t make his bandmates happy. In those days, guitar feedback was seen purely as a technical fault. Jimi tried to harness feedback for musical purposes even back then, laying the foundation for some of his signature techniques later on.

The JHS Show, "The Technology of Jimi Hendrix" (published April 8, 2022)

In May of 1966, Jimi borrowed a pedal from his bandmate: the Maestro fuzz tone, the first fuzz pedal ever created. Hendrix couldn't afford one, but he was playing in the Chitlin Circuit with Curtis Knight and the Squires, so he got to borrow this for a couple of weeks. As a result, he got his first taste of experimenting with feedback and loud sustain. Pretty soon, he was working it into his routine. Unfortunately, the band didn't like it. You have to understand that up until this point in music history, feedback was a technical error. You didn't want feedback, and you definitely didn’t create that effect with your guitar on purpose.

Jimi didn’t care. He had created this new, live sound that was really crazy, and he liked it. There's a photo of Jimi in New York City at the Cheetah Club, and you can see the Maestro Fuzz Tone sitting at his feet. So the first fuzz ever is manufactured in ’62. It reaches Hendrix four years later, and he gets his first taste of fuzz.

According to Guitar Lobby, Jimmy used FZ-1.

Glen Buxton used the Maestro FZ-1 Fuzz-Tone to achieve the distinctive "computer modem" sound on tracks like "Lay Down and Die, Goodbye," "Shoe Salesman," "Refrigerator Heaven," and "Below Your Means" from the "Easy Action" album. This pedal also contributed to the "crushed" sound on "Return of the Spiders" and "Still No Air." The Maestro FZ-1 Fuzz-Tone can be heard in live performances of "Eighteen" from 1971, as showcased in the ReelinInTheYears66 YouTube video. Its unique tone resembles the saxophone sound from the 1962 demo 45 for the Maestro Fuzz Tone.

Featured in this June 8, 2013 Instagram post. This September 10, 2013 Instagram post shows that it was used with The Budos Band.

the original fuzz tone @rico_reese @homer808 @budosbat

Mentioned and pictured in this April 2012 Vintage Guitar interview. According to this November 2009 Guitarist interview with Gary Hurst, Flick gave his unit to Hurst for modification, becoming the basis of the Sola Sound Tone Bender.

Guitarist, November 2009, "Bend It Like Beck Can"

“Vic Flick walked into the shop with his Maestro Fuzz-Tone and said, Listen, I can’t do much with this – can you have a look at it for me?” says Hurst. “I’ve still got it actually – he never took it back! Anyway, I took it to pieces, but I couldn’t get any more sound out of it than it was already making, that is until I modified it. And then I said to him, I could build you a better one.

“I’m not trying to hide anything here, the Tone Bender was based on the Fuzz-Tone, but that’s what things were like back then.

Vintage Guitar, April 2012, "Vic Flick - 007 Guitar Man"

In the studio, I rarely changed volume, as the sound man had all his knobs adjusted for the mix. Mostly, I used a DeArmond pickup through a DeArmond pedal and then into a Fender Vibrolux amp. I purchased the Fender amp in ’62, just prior to the Bond recording that June. There’s a picture of the amp and an original Maestro Fuzz Tone pedal in my book. I did have a 15-watt Vox at the time, but it fell off a stage.

On his website, Michael Monarch stated that he used a fuzz box that had "Distorto" written across the top. This is most likely referring to the D&M Co. Distorto Fuzz pedal, which was essentially a copy of the Maestro FZ-1. This pedal was used in the first and second Steppenwolf albums.

Mentioned in this February 22, 2016 Ultimate Guitar interview.

In 1966, you did the music for "The Wild Angels" film and the "Blues Theme" was written. Had you been thinking about creating a more distorted/fuzz-driven guitar sound?

I was definitely thinking along those lines because of it being a biker film.

Was it a conscious thing to get away from the clean, reverb-drenched surf guitar sound?

I wasn't a fan of the reverb and didn't think the word "surf" fit. But yes, I wanted to make a drastic change from my '63 to '65 sound.

Can you talk about those early days experimenting with fuzz sounds?

I was only using the Gibson Maestro but not doing much with distortion until the Mosrite Fuzzrite came along.

(...) In 1964, the Rolling Stones had recorded "I Can't Get No (Satisfaction)," which featured that Keith Richards fuzz guitar. Were you aware of this song? Was this the first time fuzz guitar was really used on record (Keith says it was)?

My first fuzz was the one he used: a Gibson Maestro. The first tunes I remember with distortion were "Don't Worry" in 1961 by Marty Robbins with distorted bass and "Zip A-Dee Do-Dah" in 1962 by Bob B. Soxx & the Blue Jeans.