Structure information on picture within a GOP of a coded data sequence is acquired beforehand. When subjected to pressure the prongs of the carrier mold flex to completely or substantially close one end of the carrier mold. The vertical support members have cavities on their inner surfaces, and the horizontal support members have protrusions at their ends corresponding to the cavities. In the case where the bit sequence of the data and the marker for determination is decrypted, the detection of the valid bit sequence is determined, while the detection of a dummy bit sequence is determined otherwise.