Scanning probe spectroscopy of 2D topological nanocrystals in the shell-tunneling regime (states empty) will reveal the energy of the single-electron topological gap, the energy of the helical state and the spatial extension and orbital character of the edge states. Otherwise, signatures of state-filling below that expected for equilibrium indicates charge leakage from the helical state into the bulk or environment. Hence, from advanced scanning tunneling experiments, a first idea of the robustness of the quantum spin Hall state and its electronic isolation can be obtained.