Full Bell Lines is a grading attribution for the Franklin Half Dollar series. It refers to the horizontal lines running across the bottom of the Liberty Bell on the reverse of the coin. Franklin Half Dollars exhibiting Full Bell Lines (FBL) will generally display uninterrupted lines, indicative of a fully struck coin. In many cases, coins receiving the attribution will sell for many multiples of the price of a coin without the attribution.
Third party grading services PCGS and NGC both attribute Full Bell Lines as "FBL" on their holders. In order to receive the designation, PCGS requires the coins to exhibit complete, uninterrupted lower lines on the Liberty Bell. NGC requires a higher standard to receive the designation, requiring all six lines (upper and lower sets) to be fully visible.
In general, the grading services will allow a few marks across the lines as long as they do not disturb the continuity of the lines. Slight incompleteness is also generally allowed just to the left or right of the vertical crack in the Liberty Bell within a measure of 1/64 of an inch.
Certain dates are extremely difficult to encounter with Full Bell Lines. Most notably, the San Francisco Mint coins after 1949 are typically softly struck without the detail necessary to achieve Full Bell Lines. A major strike rarity exists for the 1953-S Franklin Half, which is almost never encountered with attribution. 1953-S Franklin Half Dollars graded gem with the FBL designation have sold for tens of thousands of dollars. Other challenging coins to find in high grade with Full Bell Lines include the Philadelphia Mint issues from the 1960's.
