This build is considered to be a Release Candidate of Windows 3.1. A copy was available on BA for a long time, but was removed as it was supposedly made up of files from various other builds as well. It was compiled on 4th February 1992. The build is also listed in a French Microsoft KB (Knowledge base) article number 459866 along with builds 70 and 71, proving it's existence. The article discusses OLE issues when using Word for Windows 6.0 on these builds.
It is also mentioned in PX01251 which states this build was shipped to testers on 24th January 1992. Also, according to this page, the floppies are labeled with a date of January 21, 1992.
