they now assert that it is 40,000 years old. That would make it the oldest surviving piece of ground and polished stone. That technology was, it seems, used for making jewelry 25,000 years before anybody used it to make practical objects like tools.
The really controversial part of the Russian claim is that this bracelet was not made by fully modern humans, but by Denisovans. Denisovans were the mysterious early modern humans of east Asia, comparable to the Neanderthals of west Asia and Europe. The Denisovans were discovered through genetic analysis and we know next to nothing about their culture, but if they were ahead of modern humans in any way that would be big news.