This is a pair of realistic Handcuffs I designed off of a picture I found on the internet.

They feature a button activated double lock. After activating the double lock turn the key in one direction to unlock the lock then the other direction to unlock the cuff.

Note- With the double lock engaged it is suppose to keep the cuffs from tighten up but with the inherent flex of the bow from being made of plastic it can still tighten if forced hard enough. The bottom button is also a little weak so if it doesn't engage you may have to sand the mating surfaces of the pawl and bolt so they slide easier. This will all depend on your printer and settings.

Mirror these parts in your slicer for second Cuff

Handcuff_Casing.STL
Handcuff_Casing_Face.STL
Handcuff_Lock_Bolt_Button.STL
Hardware Required for Assembly
(10) #4-40 x 1/4" Button Head Screws
1.75 Filament for (3) Pins
Fur - optional ;)
If you have any questions or problems with the files or fitment of the parts just let me know and I will try to fix them.

Remember to pledge your designers if you like the service.... thanks for looking.