The definition of the internal DirectX D3DTLVERTEX object is as follows:

struct D3DTLVERTEX {
union {
D3DVALUE sx;
D3DVALUE dvSX;
};
union {
D3DVALUE sy;
D3DVALUE dvSY;
};
union {
D3DVALUE sz;
D3DVALUE dvSZ;
};
union {
D3DVALUE rhw;
D3DVALUE dvRHW;
};
union {
D3DCOLOR color;
D3DCOLOR dcColor;
};
union {
D3DCOLOR specular;
D3DCOLOR dcSpecular;
};
union {
D3DVALUE tu;
D3DVALUE dvTU;
};
union {
D3DVALUE tv;
D3DVALUE dvTV;
};
};