You can see the history below the current tag descriptions.
From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of Jonathan Rochkind
Sent: Wednesday, January 27, 2010 11:59 AM
To: [log in to unmask]
Subject: [CODE4LIB] marc documentation?
I know I've seen documetnation on the LC site before for since-abandoned
marc bib tags, like 400. But I can't for the life of me find it now
navigating around the website or googling. does anyone know where this is?