The following is a release from Numismatic Guaranty Corp.:
Numismatic Guaranty Corp. has added early federal gold coins to the
series that it will recognize comprehensively by variety numbers. All
quarter eagles, half eagles and eagles struck prior to the August 1,
1834, weight reduction may now be submitted to NGC under its
VarietyPlus Service to receive Bass-Dannreuther numbers.
These early U.S. gold coins were a specialty of the late Harry W. Bass Jr., and his variety studies in
this field were published as a sylloge by his research foundation in
2001. Numismatist John W. Dannreuther then added the few varieties
that Bass lacked to create a complete catalog of all die marriages,
titled Early U.S. Gold Coin Varieties. It is from this
reference that early gold coins are now attributed by BD varieties.
Submitters who wish to have their 1795-1834 U.S. gold coins
attributed by BD numbers may do so by selecting NGC’s VarietyPlus
option on the submission form. A fee of $15 is charged for this
service above the selected grading tier. For those dates having only a
single die marriage, the BD variety is applied automatically at no
additional fee. A complete listing of BD varieties, detailing those
that require a fee and those that do not, may be found here on the VarietyPlus webpage.