Eastern Zhi's duplicating machine -----------------------------5.000 square metre -----------Dust proof the earth level ground
That the southeast in Changzhou unities delivers the circle ---6.000 square metre -----------The dust proof and provide against the static electricity the earth level ground
Ou Chang optics -----------------------------------------------10.000 square metre ----------Dust proof and the earth level ground
The will of Heaven circle --------------------------------------5.000 square metre -----------Dust proof level ground
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