That stamp from a closed Ohio brass works is the real find there. Had a similar thing with a cast iron skillet I grabbed for $8 at a church sale, turned out it was an old Griswold and folks online were asking $200 and up. Never sold it though, still cooks eggs every morning. The flea market folks just want stuff gone, they don't care about the collector markup.

Did you ever stop and ask why the guy who failed him trusted that test?

That breathing thing is real. I've killed a bunch of sealed setups by never opening them. Now I just leave the lid cracked a little or pop it open every couple weeks for a few minutes and that fixed most of my rot problems. The charcoal and drainage rock layers are mostly upsell, a normal potting mix with some perlite mixed in does the same job. Pothos is also just hard to kill, it'll grow in a coffee can or a ditch.