  Some aspects of description of the Bohr-Weisskopf effect in hyperfine
splitting of the H- and Li-like ions of 209Bi are considered by application of
the surface and volume models of the nuclear currents. Extension of these
models, used in internal conversion theory, to description of the HFS allows
one to successfully describe the effect, without resorting to the specific
differences. The latters are shown not to be needed at all. Moreover, they turn
out to depend on the nuclear model even stronger than the HFS values
themselves. Comparison of the calculated HFS values to experiment shows a
satisfactory agreement. Both models provide equally good description of the
effect. However, they result in different values of the retrieved rms radius of
the nuclear magnetization. In this respect, situation resembles the proton
radius puzzle. Prospects of future research are discussed.
