"Field Service Advice (FSA) is case specific advice provided to examiners by the Associate Chief Counsel. FSA does not represent a final determination of the Service's position, even in the case for which it was requested." (Requests for Field Service Advice, I.R.M. § 220.127.116.11.1.3) The IRS has phased out FSAs.
The Westlaw scope notes say "FSAs from 1976 through 1991 are irregularly present in the database. Coverage begins in 1992 and concludes with February 27, 2004, with one document dated May 11, 2013.
Lexis Advance has FSAs from 1992 through 2003, with selected documents back to July 1983.