@Override
    public String toString() {
        return "FBXFile[version=" + version + ",numElements=" + rootElements.size() + "]";
    }
Between file versions 7400 and 7500, the FBX block sentinel was reduced,
from 13 bytes to 9 bytes.

@return the number of bytes in the block sentinel (&ge;0)
jme3-plugins/src/fbx/java/com/jme3/scene/plugins/fbx/file/FbxFile.java