Kombat Chain Link Professional Cheap Yet Decent Handcuffs
These are some cheap Kombat handcuffs from eBay in the UK. They are made in Taiwan and likely a generic brand, sold under the Kombat brand name. They cost me about £11 delivered and are surprisingly good for what you are paying for.
They have 2 pawl bars, which is good and unexpected for cheap cuffs in most cases. Although the internal mechanism leaves picking them open easy due to the positioning of the ledge inside where the key meets.
They are pretty smooth in operation, the rotating arms are aligned nicely and don't bash into the sides of the cuff and they are of a riveted construction so they are pretty sturdy. Normal handcuff keys (such as Peerless keys) do not fit (they won't turn) because the internal depth space is not tall enough to accommodate tall keys, so if you have other cuff keys, you may need to file the bottom of the key a bit to shorten the height of the bit on the end.
Over all they are quite nice and a decent pair to give to responsible kids, for bedroom use etc. Although the packaging marketing states they are designed for official police use, they are not specifically independently rated for official police use, so I would not recommend them for police or even security use. I suppose you could use them for security use as long as you're able to use what ever cuffs you want to, but the fact that typical cuff keys do not fit and there's no ditched jaws meaning a very strong person could bend the double strand and disengage the rotating arm's teeth from the pawl's teeth, I would not recommend it.
All in all, a cheap decent enough pair of cuffs for young or adult play, learning lock picking, home defence, bug out bags etc of cost is an issue. If you want a really good pair (in the UK), a pair of TCH model 800 would cost you under £30 and then you'd have exceptional quality and secure cuffs.