BD-1 is the only 1800-dated Half Eagle with a Pointed 1 in the date. "Pointed 1" refers to the upper serif (or "flag") of the 1. All other 1800 Half Eagle varieties -- and all Half Eagles until 1804 -- have a Blunt 1 on which the flag had broken off the 1. Numismatic expert, John Dannreuther, believes that the punch for the 1 broke when this die variety was made. Even further, Dannreuther notes that one of the 1799 Half Eagle varieties was struck after the 1800 BD-1, based on die state evidence.
We know of five different examples plus two or three more possibilities. Two are Mint State. A new PCGS AU55 example appeared in early to mid 2016. While collectors of early U.S. gold die varieties are few, the 1800 BD-1 Half Eagle remains a very rare coin.