This is a finished work hub. The significance of the six slots is that they form turning lugs on the struck work dies. Those lugs are used during the turning operations to keep the dies centered and spinning during the turning processes.
Even before the public design competition to select the common concave obverse for the three-coin 2014 National Baseball Hall of Fame commemorative coin program was over, Steve Antonucci, the U.S. Mint’s manager of Digital Process & Development, and his associated team were busy strategizing and testing ways to accomplish the legislated goal.
For the various test and experimental strikes needed while testing production processes, the Mint used a pool player design for the obverse and an 8-ball reverse design. The dies used for such early strikes, not intended to be used in regular production, are often called “nonsense dies.”
Once artist Cassie McFarland’s baseball glove design was approved for the common concave obverse, that approved design was incorporated within the tooling development.