"Badge engineering or rebadging is the application of a different brand or trademark to an existing product (e.g., an automobile) and subsequently marketing the variant as a distinct product. Due to the high cost of designing and engineering a new model or establishing a brand (which may take many years to gain acceptance), it is less expensive to rebadge a product once or multiple times than to create different models. The term is a misnomer in that little actual engineering takes place."
Badge engineering - Wikipedia, the free encyclopedia
What other definition do you think we should use? One that calls a Pentax-made lens with Pentax-designed optics a "Tokina rebadge"?
By the way, here's the patent for the 16-50:
Espacenet - Original document
And this one, for the 50-135:
Espacenet - Original document
Asignee: Pentax Corporation.
Now, tell me, by which standards are those Tokina rebadges?