The photos aren’t the clearest, but you can make out the E9791 marking. That is the special permit (used to be exemption) for PST high-pressure steel tanks. If so, then yes: it’s a PST tank.
The photos did not seem to include the fill pressure, but given the visual neck size I would bet big money that these are ‘true HP’ 3500 PSI tanks with the ‘narrow’ 7/8” neck. That also lines up with the 300 Bar valve this tank has. (Note: yoke cannot be used with these tanks — they are DIN only.)
ETA: I originally thought the born on date was 3/90, but after re-looking, I think it’s actually 3/95. That is in line with my understanding that this line of tanks was introduced in the mid-90’s. Either way, this agrees with this being a 7/8” DIN-only tank.
Has this tank been painted/coated? There seems to be a coating of some sort over it. And I think the markings are hard to read because they’re somewhat filled in. But hard to tell from the photos.
ETA2: I think after the 9791 you can see a “-35”. That would be the 3500 service pressure which makes it officially a “true HP” DIN-only tank. But *boy* are those markings hard to read! I’m now real curious about that added coating…