2011 - Article: The Hang: No it’s not an UFO it’s one of the most cool percussion instruments ever!

http://coolmusicinstrument.com/hang-no-its-not-ufo-its-one-most-cool-percussion-instruments-ever

“Metallurgical and acoustic research by the makers has led to significant changes and refinement in structure, design, and process over the years since the first Hang was offered.”

Note: no exact publishing date is mentioned at this article (2011 was the first capture by waybackmachine)