MSA, 1976 Official Wiffle Ball Disc, 2.5 inch, 5 INCOMPLETE sets of 79.  Each set is missing Bert Blyleven.

These sets are in mint condition and have never been distributed to the public in any way.  They are part of my private collection, gifted to me back in 1977 by MSA.  This set makes a unique and hard to find addition to anyone's baseball collection.