Pressed into service recently to teach handcuff escape workshops to high school students, I built this. The huge, functional, see-through demonstration handcuff.
Learning how the ratchet and pawl mechanism works helped the students visualize the internals of the standard-issue cuffs; they were soon shimming their way out of behind-the-back cuffings using only a hair clip.
More info on the huge demo handcuff here.
