A popular grade is A-C EXT, which has one paintable surface and can be used outside.
Type A-A EXT is also available if both sides will be exposed.
Plywood siding is also available, and comes in standard patterns such as texture 1-11, reverse board and batten and others.
A “shop-grade” panel is one that, after its manufacturing process, failed to meet the specifications of a specific grade. The piece can still be used for some applications, but should not be recommended for structural applications.
A “mill certified” panel does not carry the approval of a quality control agency, but may be used for non-regulated projects such as storage sheds or shelves.