One of the most damaging things that you can add for a tank's painted finish is a mesh "protector". That which was designed to protect the paint destroys it.
I've sourced a ton of tanks off of Craigslist and FB Marketplace. Ususally tanks that folks got sold when they did their OW course back in the 1990s or double-oughts. Then they did their one and only trip to CZM and all their stuff sat in the garage for 20 years gathering dust. The tanks never got wet (and no, those are not "new" tanks just because they never hit the water so Mr. Former-scubadude, they are not comparable to new tanks for your pricing estimates).
Back to finishes: throughout the year there are temperature variations that I'm convinced make the tanks expand and shrink ever so slightly. The combination of the size variation and the dirt being held against the tank act like sandpaper on the paint finish. When I remove the mesh, it looks like the tanks are covered in scales as that mesh pattern is now ground into the paint.
I can (and usually do) spend several hours with automotive rubbing compounds of various grits polishing them out. But it is a royal pain in the A$$. But I get a cheap new tank out of it, compared to if I were to buy new.
