The REAL HP tanks are 3500psi (stamped on the neck) w/ 7/8 valve.
The new "HP" tanks are rated 3442 psi which in reality they are a LP tank with a DOT exemption. That explains what "DA Aquamaster" mentioned before.
From the Fill Express/Dive Gear Express Website...
X-Series Steel SCUBA Tanks by Worthington Cylinders - Dive Gear Express
Many experienced divers have preferred low-pressure cylinders because they are easier on regulators, have no short-fill concerns, and are more suitable for partial-pressure blending. More recently, the low-pressure 3AA cylinders (2640 psi, i.e., 2400 with a +) are being replaced by the new DOT exemption cylinders (3442 psi, no plus needed). That's because you can use the high-pressure 3442 psi cylinders as low-pressure 2650 psi cylinders if you prefer, simply by under filling. The 3442 psi DOT Exemption cylinders have the same length, diameter, and capacity at lower 2640 psi pressure as the 3AA cylinders. Even better, the empty weight of the new cylinder design has been reduced slightly, yet the buoyancy remains slightly negative when empty.
Cylinder...............2640 psi....3000 psi....3442 psi
X7 Steel 80...........64 cu. ft.----72 cu. ft.----80 cu. ft.
X7 Steel 100.........80 cu. ft.----89 cu. ft.----100 cu. ft.
X7 Steel 120.........96 cu. ft.---107 cu. ft. ---120 cu. ft.
X8 Steel 119.........95 cu. ft.---107 cu. ft.---119 cu. ft
X8 Steel 130........104 cu. ft.---117 cu. ft.---130 cu. ft.