In a preferred embodiment, a multi-level elevated stack of planting containers is mounted to vertical support pole. A data item and one or more conditions are separately hashed, the resulting digests are concatenated, and the concatenand is further hashed to produce a final digest. An AE control section generates a brightness histogram of a preview image which is obtained by a CCD. Within the channel formed by the shaft elements, an optical probe may be accommodated from which the shaft elements may be removed by separating the two shaft elements from each other. A bobbin with an embedded multi-pole ring magnet and a coil is inserted into the bearing bore in the hub. The puller bar is internally coupled to the studbolt.