Thank you Rick,
I have assisted to the final trimming and (silver) rivet fixation, as also required by the smith. The new silver was shining and i asked him to darken it; he goes to an interior section and comes out with the thing completely dark. I tell him not so much and he rubbed it hard with a soft (flanel) cloth. Then i asked him what to do if i wanted to revert either process when i got home and he tells the trick; to darken, give it bleach, to lighten it, rub it with the cloth
.