| 摘要 |
A hollow molded article such as a ball of the kind used in play areas where children jump on and swim through a volume of the balls. During molding, date coding is impressed on the balls in a way which enables the older balls to be identified and replaced when necessary. The date coding is provided in two ways, one is to provide an adjustable pin within a part of the mold cavity, and the other is to provide indicia whose positions can be changed by rotation of the air venting plug within the mold.
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