$20 1999 FRN from CLEVELAND. The only district affected by this particular mistake. In fact, the absolute sole occurance of any type of engraving error on any big head design of any denomination.
Scarce ENGRAVING ERROR with the black "D4" set at 3mm (rather than 3.5mm). Although the differnce sounds minor, the appearance stands out immediately.
In total, far less than 50 pieces are known in all states of preservtion, with none known in CU.
This is listed as an R-8 mistake in the 3rd edition of United States Paper Money Errors by Frederick J. Bart, where it carries a value of $500 in EF.
Please note: in the illustration, a normal note appears on the left (as a reference only) and an example of the engraving error appears on the right. The actual note you receive will vary by serial number from the one shown.
A truly unusual opportunity.
Note grades PMG VERY FINE - 25.