[Arran]

In most cases they used some form of French walnut either straight or quarter sawn, sometimes they used stump or burl walnut but not usaully on a top I think that the best thing to do, if it's book matched, would be to cut a straight line parallel to the grain where the veneer splintered off and butt join a new strip (one with a similar colour and grain) along the back side. The Albert Constantine company has a gallery with photos of the various species of veneers they have available, it may help to identify what species was used in the top.
Regards
Arran