Speaking of bad welds on chains. One of the easier way to break chain cuffs is to bind the chains and then use them as a pivot point to break the chain or swivels. Bad welds on chain make binding the chains a lot easier.
Here's a pair of black S&W 100's with a bad weld on the left chain link, and TCH handcuffs with really bad welds on both links.
Here's the TCH cuffs with the chain bound. The bad weld makes this really easy because the cheek plates on the cuffs are biting into the bad weld.