Here are the two varieties I use, plus a bonus
First, Zhenjiang Vinegar.
This is a 6-year old. It is my go-to black vinegar.
Then the Shanxi version
陈醋 (chén cù) means 'mature vinegar'. This is favourite in dips with jiaozo or wontons etc. Here we have a three-year old version, as marked by the 3年 badge, 年 (nián) meaning 'year'.
Finally a third high quality black vinegar, this time from Sichuan. Baoning vinegar (保宁醋 (bǎo nìng cù) is the Sichuan cook's first choice.
I have no idea about the international availability of these particular brands. Baoning may be the hardest to find.