Yamaguchi Handcuffs?

I just got this one in for my collection. The seller had no knowledge of what it is, but believed it was from WWII. I did some reseach and have found the chain size and configuration as well as the overall shape to be, possibly, a Japanese handcuff. I believe this is a Yamaguchi handcuff. There is what appears to be a few numbers from a serial number above each of the swivels. I am not familar with the Yamaguchi cuff having serial numbers? The surface of this cuff is very worn. The markings from the company may have been worn completely off. I am stumped. Anyone have any ideas on what this one is? The key is not the original. It will open the cuffs but is smaller than the key hole and smaller than the hole for the peg at the end of the key. The swing arm is thick and the cuff is overall nicely made and has some weight to it.
-Richard Knip-

Nice looking interesting set

Lars’ Yamaguchi pic matches this one, specifically two size chain links but the tip of the ratchet looks different, like it’s cut at a different angle or blunted. Except for that they look identical.

Your set is very close to mine but not exactly the same shape to the lock house.  The lock house on my set is more rectangular.
I've always referred my set to be a Yamaguchi but who knows as there are no markings?

I just noticed the both key holes have different shapes. I'm still sure these are Japanese, Yamaguchi or not...

Lars

I was way off. Just noticed Lars’ has right and left cuffs.

I dont know for sure? Perhaps mine is an earlier version of the Osaka-Yamaguchi cuffs? I compared mine to this one on https://www.blacksteel.com/hcs/index.cg ... collector= The page says it is from Joseph Fox's collection. It also is a one sided cuff, like mine.
-Richard Knip-