Sure looks like a 90 (Rebour treated model) to me. I can't explain why it would weigh less than the published specs (except you're lucky) or why it has no number (except it may have worn away, they do that). These pics of a 90 Rebour from the wooljersey site look very similar, even has that tricolore decal on the cantle:
http://www.wooljersey.com/gallery/v/...N1433.JPG.html