From what I'm reading you have found a coil of PEX tubing in your garage and your trying to identify it. There are a few tips for identifying PEX piping, for one you stated that the coil you found has a matte surface, this automatically rules it out from being oxygen barrier. Oxygen barrier PEX has a glossy surface and is always sold in a white, red, or orange color if it is PEX-AL-PEX. The markings on the tube are usually how you determine what type of PEX it is, but there is always alternative options. Non-barrier PEX is easy to specify due to its matte look, and the colors only determine if they are for hot or cold lines.