Despite what uneducated Ebay sellers say, those US-marked horseharness trace-chains are definitely NOT from the civil war. They are from the Spanish-American War era on through World War one and beyond.
As an example of that fact... a farmer friend of mine has almost a dozen of the US-marked trace chains in his grandfather's barn. When the US Army got rid of its horses in the 1930s, the surplus horse equipment was auctioned off to military-surplus dealers and sold to the public.
For anybody here who doesn't know what a trace-chain is, in the drawing below, see the chain at lower right.
The one found by Southernrelics is the same basic form of trace chain as those with a US marking on the metal swivel... but his has a tag marked "Guaranteed"... which strongly indicates it was made for Civilian usage, not Military.
Has anybody here ever seen a civil war Military-usage relic marked Guaranteed? In my 40+ years as a digger and dealer of civil war, I haven't. Ha anybody else? If so, what kind of civil war relic was it?