Abstract
The authors discuss the Dirac-bracket quantisation procedure for the nonrelativistic rigid rotator. In cartesian coordinates this system exhibits two important features which are also characteristic of the nonabelian gauge theories, it is constrained, and nonlinear. By comparing to the known solution in polar coordinates the author demonstrate that simple hermiticity conditions are sufficient to allow the unambiguous application of the Dirac quantisation method to such nonlinear dynamical systems.