Ron, There is no list header like that, but you can get the same effect
by using
 
* Default-Options= (option1),(option2),... etc..
 
So, you need to put Default-Options= REPRO at the list header.
 
About the undocumented stuff, here is the list for the LISTEARN 1.0:
 
SET          listname <options>                Alter your distribution options
                                                for a given list
                   Mail/NOMail                 Toggles mailing from a list
                   Files/NOFiles               Toggles files from a list
                   ACK/NOACK/MSGAck            Sets acknowledgment sent for
                                               mail that you send to the list
                   REPro/NOREPro               Toggles copy-to-yourself of
                                               the mail you send to the list
                   FULLhdr/SHORThdr            Toggles the type of mail header
                                               FULL includes Message-ID: and
                                               Newsgroup: tags
                   CONCEAL/NOCONCEAL           Hide/Reveal yourself from the
                                               "REView" command
 
Regards, -turgut