It’s possible that 168 refers to sunglasses directly.
According to Google, “168” is a model number used by various, often higher-end or specific brands. E.g., “Maui Jim Typhoon” (model 168-02 or 168-10), which is described as a popular, best-selling sports frame with a “classic style” that has been in circulation since 1994; or Wilde Sunglasses (168 Model), handmade in Barcelona, Spain, and known for their timeless, durable design.
It seems to be common for high-end brands to have a model “168” among their most popular offerings. Thus, “Generic/Fashion 168” sunglasses generally refer to affordable, mass-produced, or fast-fashion eyewear designed to follow current, trendy styles.