“Full Steps” is a grading designation used for regular strike Jefferson Nickels which have at least five steps visible at the base of Monticello on the reverse. In order to receive the designation, there must be no disturbance of the steps due to strike weakness, contact marks, or planchet problems.
Full Steps Jefferson Nickels are valued at a premium to comparable grades without the designation. For certain issues, coins exhibiting full steps can be extremely rare and carry enormous premiums. For modern issues of the series after 1986, coins with full steps are generally easier to find. The image on the right is a 1973 Jefferson Nickel with Full Steps, while the image below is a 1999 Jefferson Nickel with Full steps.
The major coin grading services PCGS and NGC both use the abbreviation “FS” to designate Full Steps. Only regular strike coins graded MS60 or higher may receive the designation. PCGS has always awarded “FS” for coins displaying either 5 or 6 steps. Initially, NGC only awarded “FS” for coins displaying 6 steps. Starting from February 16, 2004, NGC refined their qualifications and began using the designations “5FS” or “6FS” based on the number of complete sets visible.
Some particularly difficult Jefferson Nickels to find in gem condition with full steps include 1953-S, 1961-D, 1962-D, 1963-D, 1969-D, 1970-D. In each case, three or fewer of coins have been graded as such by PCGS or NGC. There are some issues where an example has never been graded MS65 or higher with full steps, such as the 1967, 1968-D, and and 1969-S.
taken from: http://jeffersonnickel.org/