Pens are packed 12 pieces to a box and 200 boxes to a wooden case.
请问:12 pieces to a box是方式状语吗?200 boxes to a wooden case也是方式状语吗?
是的,12 pieces to a box 和 200 boxes to a wooden case 都是方式状语。
其中的 to 表示单位(“每”),可视为两个短语前省略了介词 in:
Pens are packed (in) 12 pieces to a box and (in) 200 boxes to a wooden case.