This build is mentioned in Microsoft antitrust document PX01251 from February 1992.
All release candidate builds in that document are simply referred to as "RCX" and not by their actual build number. A file from build 101 is versioned "3.1.0.101 (RC1)", so the RC1 referred to in that document must be a later build than 101, or at least a recompile of it. The document also states this build was shipped to testers on 14th February 1992.
