The 050 field – Library of Congress assigned LC call number.
In most cases KU uses the call number in the 050. Even if the 050 call number is not being used a our local call number, do not delete 050 fields. If the record does not include a 090 or 099 field, ALMA will construct a holding call number from the 050
The 090 field – Locally assigned LC call number.
In some cases the LC call number listed in the 050 field is not the desired call number. The call number may be in a classification section that we do not use; it may have two subfield “a”s; or it may be incomplete – lacking a cutter number and/or a date. In these cases an alternate LC call number is constructed in a 090 field. When a record has both a 050 and a 090 field, Voyager derives the holding call number from the 090 field – not the 050 field.
If the 050 has an “x” after the cutter number, delete the “x”
Keep the rest of the call number as it is. The “x” means that there is another book with the same call number in the LC collection. The likelihood that we would have that other book is very low, and if we did have it we would change the cutter number.
If the 050 has a letter after the date, keep the letter.
A “z” after the date means that the date is questionable. Questionable dates should be reflected in fixed field and the 260 -- most likely with a question mark. If the 050 has a letter other than “z” after the date this letter indicates that there is another edition of the item that was published that same year.