This is one of the original Stanley Cup rings.
It belonged to Billy Barlow of the Montreal AAA (Amateur Athletic Association). The AAA, also known as Montreal Hockey Club, were the first winners of the Stanley Cup back in 1893 - that's 24 years before the NHL even existed!
This ring resides on display at Hockey Hall of Fame. The only other 1893 ring known to still exist sold in 2009 at auction for about $60,000. It belonged to George Lowe.
I'm still trying to find much information about Mr. Barlow. Apparently he was a spectacular skater, blessed with agility and nimbleness unlike most of that era. He was instrumental in the Montreal's final win of the season over Ottawa to secure the Stanley Cup's inaugural championship. The following year Barlow was credited with scoring the first Stanley Cup-winning goal in history in the final playoff match of 1894. He actually scored twice in that game and was heralded as the top player of that.
You can read the actual newspaper account of the first Stanley Cup championship at Library and Archives Canada's website. Robert Lefebvre of Eyes On The Prize also has a good feature.