These were all made by Autech in limited quantities. Autech is a company wholly owned by Nissan Japan which is known to make special variants of Nissan vehicles for niche markets. Like the RB26DE four door non turbo auto R32, the RS260Stagea.
These were produced to celebrate 40th anniversary of the Skyline. Here's the official Autech website about them: http://www.autech.co.jp/HISTORY-SV/R33S01/index.htm
Recently they have been putting their name to different trim levels of standard cars, V35 Skylines and M35 Stagea's. Don't really see them doing anything too bold like they used to though.