Chuck mechanism and top jaw

A chuck mechanism comprising:

• a chuck body including an installation surface and a side surface;
• and
• a master jaw provided on the installation surface of the chuck body and configured to move in a radial direction of the chuck body, wherein a first marking is provided on the installation surface of the chuck body, the first marking is product information of the chuck mechanism, the product information of the first marking includes at least one of information representing a model number of the chuck mechanism and information representing a serial number of the chuck mechanism, the information representing the model number and the information representing the serial number include at least one of a letter and a number so that humans can understand at least one of the model number and the serial number when at least the one of the letter and the number is visually recognized by the humans, at least one second marking is provided on a peripheral side of the installation surface or the side surface of the chuck body, the at least one second marking is a two-dimensional code that does not include the letter and the number, and the second marking includes the same information as the product information of the first marking, wherein the installation surface of the chuck body is configured so that a jig for workpiece machining can be attached, an area of the installation surface of the chuck body that is processed when the jig for workpiece machining is attached to the installation surface of the chuck body is defined as a processed area, an area of the installation surface of the chuck body, excluding the processed area, is defined as a non-processed area, and the at least one second marking is provided on the non-processed area.