Looks like it's the real deal. My response from ACO below when I asked about the dates for 2005.
Dear Sir,
The date should be the 18 and 19.06 under reserve of the publication of the federal calendar.
Yours faithfully.
Le Service Réservations / Booking Office
Circuit des 24 Heures du Mans
72019 Le Mans Cedex 2
Fax: (0033) (0)2 43 84 47 13