Generally also there are indeed some varieties out there such as a 1972-D No FG Half Dollar should show no traces of Gasparro's initials. Genuine No FG halves will also show weakness in other surrounding features, such as the eagle's wing, stars, etc. While absence of the FG initials can be picked up by the naked eye, use of a high-quality 5X or 10X magnifier is ideal, particularly for ruling out what may actually be a weak FG, which isn't presently a recognized form of this variety unlike the No FG. You can find this and others in a book called Strike it rich with pocket change 5th edition, or on the forum and free online sites if you wish to regularly search coins for possible varieties and errors that may have some added value.