i mean as the same gun being used by two people at once
Chances are strong that the fire extinguisher firms are quite legitimate. When firms are located near state lines, it is very common for them to be licensed in the nearby states, so that they can do business across those state lines. If you're that concerned about it, simply phone the company in question and ask them.
When the transformer behind my house caught on fire, the fire department called the electric company and had them shut the power down for our grid before they put the fire out.
