WHAT IS IT? 🤔 - Need Your Help - Weird Bar Handcuff - Unknown

WHAT IS IT?
Weird Bar Handcuff - Unknown

Hey all does anyone have any clue what this may be or from what country?

I have google image searched and tineye searched all showing nothing resembling it.

I think its a handcuff. Im thinking (speculation of course) that it might be from Austria or one of the countries that made Dollar Sign Cuffs because it sorta has that early vibe.

The Cuff's dimensions are approx:

Length = 5.5"
Bar thickness = 3/4"
Bow thickness = 5/8"
Overall height = 3 1/2"
Weight = 1.25lbs
Hex key 6 sides = 8mm

I'VE GOT OTHER WEIRD HANDCUFFS TO UNVEIL TO GATHER ANY INFO. SO PLEASE LET ME KNOW YOUR THOUGHTS AND THEORIES.

What metal is it made of? Looks home made. 

its magnetic i dont know if its steel I'm not a metal guy  I've had some homemade items I am leaning towards this not being homemade just from the feel and construction up close

Thanks for the added info. The main reason I said 'home made' is that all material are stock sizes. A better term than home made is customised. If it was a commerial item where thousand are made, the round shackle would have be likely cast and not welded. Is it a hex socket bolt that locks it? 

Hi
Yes. It float in side like the thread ed part of a plug 8

It the hex metric or imperial? That might give a clue to country.

Hi
8mm 

The Cuff's dimensions are approx:

Length = 5.5"
Bar thickness = 3/4"
Bow thickness = 5/8"
Overall height = 3 1/2"
Weight = 1.25lbs
Hex key 6 sides = 8mm

Must have been made after 1909 then............. 1909

W.G. Allen filed the first related patent in 1909 for its recessed hex-driven safety screws,...........................



also.....

• 1. The metric system has been adopted by most major countries around the world. By the mid-1970s, most countries had converted to the metric system or had plans to do so. When it comes to measurement, the United States is the only major country that has not adopted the metric system! Using the metric system just makes sense, in order to standardize measurement around the globe.