  It was predicted that local spin polarization in a ring of five dipolar
coupled spins should present a particular fingerprint of quantum interferences
reflecting both the discrete and finite nature of the system [Phys. Rev. Lett.
75 (1995) 4310]. We report its observation for the proton system of a
(C$_5$H$_5$)$_2$Fe molecule using a rare $^{13}$C as {\it local probe}. Novel
high frequency ($\simeq 60k$Hz) polarization oscillations appear because
incomplete $^{13}$C-$^1$H cross-polarization transfer {\it splits} the
polarization state, in a portion that wanders in the proton system and one that
remains in the $^{13}$ C. They interfere with each other after rejoining.
