To easily change a bar-code tag in a simple constitution and securely attach it.

An identification mark like a bar-code is provided at a position which can be easily found from the outside and parallelly arranged wefers are supported at the same time. And a plate-container pocket 15 formed within the wall facing the outside to contain the bar-code tag 16 and the cover body closing the opening in the state the bar-code tag 16 is contained in the pocket 15, are provided. The bar-code tag 16 that a bar-code has been already written, it can be written or it can be exchanged, is used. A white board may be contained in the plate-container pocket 15 in order to easily identify the bar-code written on the external surface of the plate-container pocket 15.