The listing, 1935F SILVER CERTIFICATE W/PRINTING ERROR (Ol' George has a "black eye") has ended.
Why Ol' Georgie has a "black eye", was most likely caused by some debris on the plate. Such errors are not unheard of, but generally speaking, such a bill (had it been identified) would have been replaced with a "star bill", so the error does make this a "rarity". I always liked the "X" on this bill: it really doesn't increase its value, just liked the "X" factor :)
The obligation of a certificate states how much of a specific commodity the government of a country will "pay to the bearer." On most large-size Silver Certificates, the obligation reads: "This certifies that there is on deposit in the Treasury of the United States of America (number) silver dollar(s) payable to the bearer on demand." On small-sized Silver Certificates beginning with Series 1934, in order to denote current location of deposit, it was changed to read: "This certifies that there is on deposit in the Treasury of the United States of America (number) dollar(s) in silver payable to the bearer on demand.
Printing of the Silver Certificates ceased in 1964, and after 1968 could not be redeemed for silver as the price of silver had increased significantly (and had some cashing in and melting down the silver coins obtained with the "paper"), and the U.S. monetary system was now based on the "gold standard".