  We consider translation surfaces in the 3-dimensional Euclidean space which
are of coordinate finite type with respect to the third fundamental form $III$,
i.e. their position vector $x$ satisfies the relation $\Delta^{III}x = \Lambda
x$, where $\Lambda$ is a square matrix of order 3. We show that Sherk's minimal
surface is the only translation surface satisfying $\Delta^{III}x = \Lambda x$.
