SoFieldConverter(3) on Linux
The text 75469b04b79c, as Debian 8 (Jessie) shipped it.
The SoFieldConverter class is the abstract base class for field converters. When fields of different types are attempted connected, the Coin library tries to find a field converter class which can be inserted between them, acting as a filter converting values from the master field to values matching the type of the slave field.