  Chemical tagging is a powerful tool to reveal the origin of stars and
globular clusters (GCs), especially when dynamics alone cannot provide robust
answers. So far, mostly $\alpha$- and neutron capture elements have been used
to distinguish stars born in the Milky Way (MW) from those born in external
environments such as that of dwarf galaxies. Here, instead, we use iron-peak
elements abundances to investigate the origin of a sample of metal-rich
globular clusters. By homogeneously analyzing high-resolution UVES spectra of
giant stars belonging to four metal-rich GCs (namely NGC 5927, NGC 6388, NGC
6441, NGC 6496), we find that while the $\alpha$-elements Si and Ca have
similar abundance ratios for all the four GCs, and Ti and neutron capture
elements (La, Ba and Eu) only show a marginal discrepancy, a stark difference
is found when considering the abundances of some iron-peak elements (Sc, V and
Zn). In particular, NGC 6388 and NGC 6441 have abundance ratios for these
iron-peak elements significantly lower (by ~ 0.5 dex) than those measured in
NGC 5927 and NGC 6496, which are clearly identified as born in-situ MW clusters
through an analysis of their orbital properties. These measurements indicate
that the environment in which these clusters formed is different, and provide
robust evidence supporting an accreted origin from the same progenitor for NGC
6388 and NGC 6441.
