https://patents.justia.com/patents-by-us-classification/428
(class / ) paper containing (e.g., paperboard, cardboard, fiberboard, etc.) (class / ) glass, ceramic, or sintered, fused, fired, or calcined metal oxide or metal carbide containing (e.g., porcelain, brick, cement, etc.) (class / ) flexible food casing (e.g., sausage type, etc.)...