I'd go with Intercept Shield 2X2s or AirTights . They're both hard plastic snap together holders , but Intercept Shield has some copper particles that will neutralize the sulfides that cause copper to turn brown . Also use desiccants . I like the ones in the small metal case with the clear hole so you can tell when they need to be put in the oven to recharge . You can find them at Wizards . http://www.wizardcoinsupply.com/products/intercept-shield-2x2-holders/
Things I've never had include: -half cent -seated Liberty coinage -trade dollar -anything gold -pre 1800 US coins There's probably other notable things I don't have one of, but I can't think of them right now.