This is an experimental piece made by the mint in 1979 to give to vending maching manufacturers to prepare for the coming 11 sided Susan B. Anthony dollars.
Examples were struck as follow:
Cupro-nickel clad J2175/P2089 with about a dozen known including the 2003 and 2016 ANA sale pieces.
Nickel J2176/P2090 with over a dozen seen.
Probably a dozen or more exist.
The top example is one of two offered in the May 23, 2001 Teletrade auction and the bottom example was offered in Bowers and Merena's June 2001 sale.
These may represent 2 different varieties with the latter having a raised center. The top example appears to be flat in the middle but this could be the result of the photographing process. We will not give them separate numbers until these apparent differences are confirmed.
Photos courtesy of Teletrade and Bowers and Merena.