  This is a supplement to [arXiv:1503.03676], where an approach towards a
mathematically rigorous definition of the Coulomb branch of a $3$-dimensional
$\mathcal N=4$ SUSY gauge theory was proposed. We ask questions on their
expected properties, especially in relation to the corresponding Higgs branch,
partly motivated by the interpretation of the level rank duality in terms of
quiver varieties [arXiv:0809.2605] and the symplectic duality
[arXiv:1407.0964]. We study questions in a few examples.
