Sometimes a national authority record just lacks some of the key information that your library needs. Maybe it’s an important cross-reference, a note, or some sort of field identifier. If you just receive the latest Library of Congress authority, for example, you could lose all that hard work that you and your staff have gone through to find the information and add it to your authorities.
This section is found in your Profile, Step 3, Question 11 (See this section). It’s pretty short – shorter than I was thinking. Basically you just need to mark the radial button and indicate what the $5 will be. Here’s a (hopefully better) explanation of what I was trying to explain:
Say you have an authority to which you’ve added a local 500 see-also reference, and maybe you’ve modified an 022 and added a 670 note. Say you want to preserve that 500, the modified 022 and the 670 field no matter what. If you add a $5[code] to the end of those 3 fields and send us a copy of the authority, we can then take those 3 fields and put them into a table here, along with the authority's control number. Then the next time LC updates that authority our system will match the control number with the table, find the fields that need to be preserved and add them to the updated authority we'll be sending to you. When you load the authority back into your system it will overwrite the one you've already got, but it'll be okay because the fields you need preserved will be in the new record. Here's an example of what I mean about marking the fields (I made up some of the info in this example - it's pretty bad - please forgive):
001 __ n 00001621
003 __ DLC
005 __ 20001227110358.0
008 __ 000204n| acannaabn |n aaa
010 __ $an 00001621
022 __ $a0743-1643$l0743-1643$5SYM
040 __ $aDLC$beng$cDLC$dDLC
100 1_ $aHester, D. Micah
500 1_ $aAndrews, Joseph$5SYM
670 __ $aComputers and ethics in the cyberage, 2001:$bCIP t.p. (D. Micah Hester)
670 __ $aCommunity as healing, 2001: CIP t.p. (D. Micah Hester) data sheet, etc. (b. Jan. 16, 1966; Ph.D., asst. prof. of Biomedical Ethics, School of Medicine, Mercer Univ., Macon, Ga.)
670 __ $aCommunity as healing, 2001: CIP t.p. (Joseph Andrews, co-author)$5SYM
The bolded stuff in the 022, 500 and 670 is the info "added" and the red info is the code you should put on the field so we know it's what you want preserved. I hope that all makes sense. 
To get this going you need to do 3 things:
(1) Decide what kind of a code you want in that $5, and then add it to all the fields in all the authorities you want preserved. Most of our other clients just use a version of their library code ... for example, $5SYM. But you can use whatever you'd like - just as long as we know what it is;
(2) Send us a copy of the modified authorities so we can create a table;
(3) Also send us a list of the fields you want preserved. Example: "We've modified some 050s, 022s, 400s, 500s, 670s - please preserve these tags if they have a $5SYM."
And that's pretty much it. Your fields will be preserved every time we receive an update from LC.
If any of this seems unclear or if you have any questions at all, please don't hesitate to ask.
Thanks to our project manager for writing that up. Preserving fields is one of the services many of our libraries find most useful, and we have even more options than listed above when it comes to preserving your data for cases where adding a $5 would be unreasonable or impossible. so feel free to talk to on of our project managers about how we can help you with your situation.
