Windows Neptune build 5067.1

One file (gemstar.sys) with version number 5.50.5067.1 and product name "Microsoft(R) Neptune (TM) Operating System" is found in Windows Millennium Beta 1 (build 2380.2), but it is unknown whether this Neptune build ever existed. If real, it would compiled between 13th June and 20th September 1999 (according to file dates) and would probably be an M1 build.