These iron manacles look old, slightly rusted, and heavily dented.

Shackles of silence fit any Small, Medium, or Large creature. A creature manacled with these shackles is affected by a silence effect (as the spell) that fills that creature’s space.
A creature can slip free from shackles of silence with a successful DC 28 Escape Artist check, or break free with a successful DC 28 Strength check. However, if the creature bound by shackles of silence escapes by breaking them or using Escape Artist, the silence effect ends and the shackles ring for 1 round, as an alarm spell’s audible alarm. Broken shackles of silence lose their power after sounding this alarm, becoming nonmagical and useless.

Prerequisites: Craft Wondrous Item, alarm, silence.
Cost to Create: 3,000 gp, 240 XP, 6 days.