Jamieson, Fausset and Brown on Genesis 38:18

18. signet, &c.--Bracelets, including armlets, were worn by men as well as women among the Hebrews. But the Hebrew word here rendered "bracelets," is everywhere else translated "lace" or "ribbon"; so that as the signet alone was probably more than an equivalent for the kid, it is not easy to conjecture why the other things were given in addition, except by supposing the perforated seal was attached by a ribbon to the staff.