Did you check all the forms, etc for Fannie Mae on the http://www.adfinet website (which is free)? Is that number listed anywhere? Although none of those letters represent anything from Fannie Mae, which in 1989 would have been FNMA. Between 1990 and 1993 there use to be an "Addendum 70" floating around, but the 1993 1004/70 solved that problem along with the reason for the multi-purpose addendum. Freddie Mac forms can only be accessed through a site that has a high annual fee.