Local historians are already describing the find as one of the most important ever in the south of Scotland.
And if their early calculations are right – the object may be a 3,000 year-old mirror.
Historical author and broadcaster Alistair Moffat was given a sneak preview of the object this week. He said: "I was absolutely astonished when I saw it. This has to be the find of a lifetime.
"There were two Bronze Age shields found near the site at Yetholm in the 19th Century. And we believe this dates from around the same time.
"But after much discussion we think this is in fact a mirror, rather than a shield. If it is, it would be the first Bronze Age mirror found in Scotland."
The find-site, only half-a-mile from the Roxburghshire village, is believed to have been the bottom of a small loch during the Bronze Age.
And priests at the time would have deposited glorious gifts into the water to appease their gods.
Borders historian Walter Elliot contacted the National Museum of Scotland after being shown the 14-inch circular bronze artefact. He said: "In all the years I've been involved with archaeology, I have never seen anything like it.
"Bronze Age finds are extremely rare for this part of the country.
"I have been searching through all the books trying to work out exactly what it is, and I'm inclined to think it is a mirror, although we will have to see what the people from the museum think.
"Whatever it turns out to be it will still be one of the best finds ever in the Scottish Borders."
Metal detector enthusiasts Alf Slingsby and Roger Elliot discovered the first piece of the object just after Christmas.
And for the past nine weeks they have been returning to site almost daily to locate more parts of the Bronze Age jigsaw.
Roger Elliot, from nearby Kelso, has been metal-detecting for over 25 years, and is convinced he has found something very special. He explained: "This is a detector's dream. I've found plenty coins and other important things over the years, but nothing as good as this.
"We have now found over 100 parts of the item, and it is almost complete. We first thought it was a shield because of the previous finds, from the 1830s.
"But once we showed it to Alistair Moffat and Walter Elliot they both thought it was a mirror.
"I have been looking at Bronze Age mirrors on the internet, and I'm now inclined to go along with their judgement. It's the right size and shape, although there has never been one found in Scotland before."
Experts Trevor Cowie and Fraser Hunter, from the national museum, are due down in the Borders today (Thursday) to cast their eyes over the find.
Neither wanted to predict what the mystery object was prior to viewing and carrying out tests.
But former mine-detector Alf Slingsby won't mind whatever the official verdict is. He said: "I only started metal detecting as a hobby a couple of years ago and this is fantastic. I spent a lot of my working life looking for mines all over the world – it's good to find something useful."