Hong Kong dollar or Hong Kong dollar is the legal tender of Hong Kong. According to the Basic Law of Hong Kong and the Sino-British Joint Declaration, Hong Kong's autonomy includes the right to issue its own currency. Its official ISO 42 17 abbreviation is HKD (Hong Kong dollars); The sign is Hong Kong dollars.

I copied the above paragraph for you from Baidu.

It means that this jewelry is 689 Hong Kong dollars, which is about 608.3348 yuan.