The 1940-D FS-101 Quarter Dollar is a very nice Doubled Die Obverse. The doubling is mostly visible on the legend IN GOD WE TRUST. Doubling is also visible on the date, but to a lesser degree. In lower grades, this variety fetches a strong premium of two to three times the price of a normal Quarter. Inexplicably, the premium drops as the grade increases. PCGS has certified very few examples of this variety, the best of which are graded MS66.
Beware -- there is at least one other Doubled Die Obverse of this date. If the doubling does not match the attribution picture above in every way, it is NOT an FS-101 and is not worth the same premium.