Can anyone help me with the origins of this unusual handcuff?

Can anyone help me with the origins of this unusual handcuff?

Can anyone help me with the origins of this unusual handcuff?. I picked this heavy brass figure 8 handcuff up the other day after a really weird, convoluted, and frankly out-of-the-blue surprise.
When I got the cuff, a lot jumped out at me, primarily the "triangle" security bolt head used to secure it.

I have several handcuffs that use this triangle bolt head, but I don't have a definitive origin story. I've always felt they are primarily from Germany, but maybe France? I have no clue,e even though I'm leaning towards Germany.

In one of the pics, I also show another figure 8 I have that came from the Tegel Prison in Berlin, which started housing prisoners in 1898. This cuff takes the key from the heavy unknown one pictured perfectly, same size bolt heads.

I have an Oregon Boot stirrup (for sale as I have no use for it) that is unusual and hinged, and all of its bolts are security triangular bolt heads, too.

Could anyone please give me more info on this, the approximate time frame and origin?

I appreciate any input other than trying to get me to invest in crypto lol.

Thank you,
Michael