Tony Iommi's official site mentions that he used a variety of amplifiers, including a Marshall JCM 2000 DSL 50, among others such as Laney GH 100 TIs and a vintage Vox AC30, highlighting his diverse amp setup.

In the linked article you can see diagram of Jeff Beck's live setup from around 2003. It includes 3 Marshall JCM 2000 DSL 50 heads, one for the main sound, 2nd as a backup and 3rd as a slave for monitors.

His tech described the main one (marked as Proto 0001 on the diagram) as being a prototype version, different from what production models are. From 2010 interview with Steve Prior (link dead, archived version), Beck's tech at the time, for Guitar.com:

That’s what people don't understand really. How can I get that tone like Jeff Beck? You can’t because the amplifier you’ll never find anywhere else. If anything ever happened to that amplifier he'd be lost anyway. There’s just no amplifiers that sound like that one. Even Marshall don't know why it sounds the way it does. There’s a couple little extra components in the pre-amp gain stage, which shouldn’t really account for the sound of the amplifier. The amplifier is more bassy than any other DSL50. There are another DSL50s that don’t sound anything like it. It’s the first proto-type, so its circa 1994. He, alongside a few other guitarists, was given that one about 10 months before they revised the circuit board three or four times and then actually put that one into production. To this day that one still survives. The other nine that everybody else had all caught fire or developed faults, went straight back to Marshall, and then they fault-found as well as they could and ended up cleaning up the circuit board manufacturing techniques.

The backup head was a production model though:

Another Marshall DSL50, but it’s nothing like the original one. It’ll only be a backup for 10 seconds while I have the back off and put new tubes in. If it’s any more involved than that, he’ll have to just play that. Any one of the spares would be [suitable, but not as good] for the rest of the show. That’s the problem. We can’t, having tried and having researched the situation at great lengths with all the designers at Marshall, they can’t find any tangible reason why that amplifier sounds different to any other one.

In the Premier Guitar "Acid Bath Rig Rundown" video, guitarist Sammy Duet is seen using the Marshall JCM 2000 DSL 50 amplifier. Duet mentions that these amps are easy to get, sound good, and likes that they feature two lead channels.

(MAMI uses) two Marshall JCM2000 50W Dual Super Lead heads running through a 280W 1960AV angled 4x12" cab and a 100W 1960AX (or possibly a 50th Anniversary) angled 4x12" cab. -SCANDAL HEAVEN

In a twitter post made by Syu on April 25th, 2018, he is seen using a Marshall JCM2000 Dual Super Lead tube amp.

Laura-Mary's main Amp is a Marshall JCM2000 DLS 50

The item is mentioned at 3:08

"I used my basic live rig: a couple of Fender Twins and a Marshall JCM2000 with a Tone Tubby cab and speakers with hemp cones. I just love them. They sound great and last a long time. It’s pretty much the same setup as when I did that Rig Rundown with you guys."

Kennedy uses a JCM2000 DSL in this live photo. This is not his usual amp setup as The Maine are usually seen playing Orange Amps.

Kengo Matsumoto uses the Marshall JCM 2000 DSL 50 amplifier. Although its appearance remains as the original JCM 2000, the internal components have been replaced with a 50-watt used amp. Matsumoto prefers its rock sound for live performances, typically setting it to crunch, though he finds it challenging to record with. This information is detailed in his gear list on Equipboard.

Spotted at 1:30s in Andy Susemihl's music video for "Aeroplane".

Preston Hazard is confirmed to use a Marshall JCM 2000 DSL 50 amp head, as evidenced by a promotional post on his Instagram where he is seen with a mic'ed setup.