Hub retouching

The sub-category of coin errors known as “hub retouching” refers to mistakes made by engravers during the hub design phase. These errors can go unnoticed until the coins are distributed to banks and enter circulation as ordinary currency. Upon discovery of such errors, production is temporarily suspended so that the engraver can correct the design before continuing with minting.
An example is the 1958 Franklin Half Dollar with Full Bell Lines (FBL). The design of the coin features the Liberty Bell on the reverse side, and the FBL designation indicates that the horizontal lines on the bell are fully struck and visible. However, some examples of the 1958 Franklin Half Dollar with FBL designation exhibit an error in which the lines are partially or completely missing. This error is believed to have been caused by a hub retouching issue, in which the hub used to create the coin dies was modified or repaired in a way that affected the final appearance of the struck coins. The 1958 Franklin Half Dollar with FBL errors are highly sought-after by collectors and can command a significant premium over other examples of the coin.

While this error was initially considered a variety, statistics show that approximately 50% of the total circulation of 80,000,000 coins were actually minted with the incorrect geographic boundaries. As a result, this design error does not increase the numismatic value beyond the standard catalog price for this coin.