  The harmonic quarks and their complete oscillators are successfully used for
the exact quantitative results and an explanation of the $D$ meson mass
differences. For the first time it is shown that the mass differences of the
charmed mesons with the same flavors are strictly quantized by the rest masses
of harmonic quarks in both "free" state and complete oscillator state. The
$D^*(2007)^0$ $\to$ $D^0$ transition has the following neutral quark group:
$d$-oscillator + $u^0$-quark with rest energy 142.124 MeV. It is argued that it
is the unique model solution within the 4$\sigma$ experimental interval. The
$D_s^{*+}$ - $D_s^+$ mass difference is quantized by the simplest quark
reaction with the difference energy 143.756 MeV. The energy of the
$D_{sJ}$(2460)$^+$ $\to$ $D_s^+$ transition explains by the decay of the one
complete $s$-oscillator with the energy 491.33 MeV. The full agreement with
experimental data of CLEO and BELLE is obtained. The problems of a quark shells
and the quantization by quark rest masses are discussed.
