Question Mysterious Cylinder Markings on Several 1988 PST HP80

[AquaticAfro]

I work at a dive shop and I happened to come across four HP80’s made by PST in June of 1988. There are a few markings on the crown that I don’t know the meaning of and I can’t find answers for online, in the PSI handbook, or from any of my bosses.

The first odd marking is a heart located below the Cochran Labs stamp on the tank.

The next odd marking is a shape that reminds me of an old fashioned keyhole (a circle with an inverted triangle on top of it). It is located at the top of the crown near the threads.

The last one that I can see appears to be an uppercase letter M with a circle around it. This is the faintest of the markings however so I could be wrong about what it actually is. This marking is located next to the previously mentioned keyhole looking marking.

I will attach photos of each of the markings to this post.

 

[Still Kicking]

They look very clean so I would guess they were done by PST at the time of manufacture (quality control marks maybe?)

There's no restrictions on additional stampings on a tank as long as they are on the crown and don't obscure the required stamps.

 

[AquaticAfro]

They look very clean so I would guess they were done by PST at the time of manufacture (quality control marks maybe?)

There's no restrictions on additional stampings on a tank as long as they are on the crown and don't obscure the required stamps.

That was my thought as well. The stamps are pretty consistent in placement and quality across all four of the tanks so that’s another thing that makes me believe that it was done by the manufacturer. I know there is no problem with them being there since it meets all the standards but I think I’ll email PCI to see if they know anything about it. I’m honestly just curious to know what they mean at this point.

 

[AquaticAfro]

Just an update, I contacted PSI/PCI and got an answer I am satisfied with. They said that the markings are some kind of internal marking system for PST. They said that since the tanks are so old it is hard to say for certain what each of them means specifically but the know that they are official PST markings. The only one they could shed any more light on was the marking that looked like the letter M with a circle around it. They said that it was some kind of internal hydro marking.