Quasi-classical calculation of eigenvalues by Maslov quantization condition — examples and question

The Maslov quantization condition can be regarded as a generalization of Bohr quantization rule. The Maslov quantization condition gives a good approximation of an eigenvalue of Schrödinger operator in general.
For several Schrödinger operators, the Maslov quantization condition gives exact eigenvalues and multiplicities.
In this talk, we discuss the Maslov quantization condition. We give some concrete examples of Schrödinger operators having such exactness, and pose a question related to these examples.