some of the nicest coins I have ever purchased are AU-58. Sometimes I prefer them. In fact, we have done entire threads on this very subject: AU-58 vs. UNC.
ended up replacing with these The guy who sold me them had no problem at all swapping them out even though I have a better understanding what BU is now I like these better ...... The lines are hair or something on the airtites still gotta get em outta them ..