1) It will be marked with E9791 or SP9791
2) It will say PST
3) The working pressure will be either 3442 or 3500
4) The tank will be gray, black, blue, or yellow
The message below is from a local forum I belong to, do your own research:
Here are very recent updates on the steel tank issue from two SoCal shop owners:
New info this am from DOT concerning the PST Scuba cylinders DOT-E9791 / SP 9197 Series with pressures of 3500 / 3442. The Exemption and CFR were slightly ambiguous and we asked for complete clarification. Exemption: No person may use or apply this special permit, including display of its number, when this special permit has expired or is otherwise no longer in effect. Quoted from DOT: "The cylinders manufactured under the terms of the special permit may not be used after the permit has expired." Also, as we stated before, on 22 Jan DOT stated they had not heard from PST concerning a renewal...
As of this morning... 27 Jan, DOT states: "I’m in communication with the grantee of DOT-SP 9791, he insists he is going to request renewal. We’ll expedite his request if and when we receive it." Soooo, in the mean time.... all hydros of tanks received are in fact on hold. The only tanks we are doing right now are those that already need or were very close to, needing a new hydro. PST is out of business, that rumor is true but it sounds like someone has purchased the rights to all PST assets... At one time when they went under, PST owed much more than assets. It appears someone is attempting to keep it alive in some fashion. (I can't release this info just yet)
I just (Tues, 1/27 @ 9:30AM PST) got off the phone with Bob Darling of PST Cylinders, LLC (which is what Pressed Steel morphed into) and he assured me that he has filed the renewal paperwork as of yesterday. He said he was having some computer issues but they have been solved and this should go through. The renewal may not get approved prior to January 31 which is when the current one seems to expire (despite the fact that website says 2/28/2015) but the gap will likely be short because, as he told me, the sooner the renewal gets processed the sooner both he and the DOT will stop getting calls about it.
This link should allow you to track the progress of the renewal. Just type in "SP9791". Bob says he doesn't think anything will show up on the website until tomorrow: PHMSA - Home
The other good news is that there's no fee on Bob's end to do this so he says he intends to continue to renew the SP down the road.