This piece is similar to the 1999 state quarters - Connecticut, Delaware, Georgia, New Jersey or Pennsylvania known to have been struck on Sacagawea dollar type planchets. This particular example weighs 100 grains and is ex Byers, Heritage 1/11 FUN sale.
Photo courtesy of Heritage.
Editor's note: It is unclear if these are truly experimental pieces or some sort of mint error. It is very possible that these were deliberately struck. We are listing them under mint errors as this sector of the collecting fraternity was the first to embrace these. We hope that further information into their true nature will appear in the future.