SoNodeKitDetail(3) on Linux
The text b8c03d18f4f4, as Debian 6.0 (Squeeze) shipped it.
The SoNodeKitDetail class is yet to be documented. When a pick action is executed and geometry within a nodekit is hit, the nodekit generates an SoNodeKitDetail object which contains information about the specific part inside the nodekit hit by the pick ray.