16 CFR 23.15 - Misuse of the term
It is unfair or deceptive to use the terms “properly cut,” “proper cut,” “modern cut,” or any representation of similar meaning to describe any diamond that is lopsided, or is so thick or so thin in depth as to detract materially from the brilliance of the stone.
Note to § 23.15:
Stones that are commonly called “fisheye” or “old mine” should not be described as “properly cut,” “modern cut,” etc.
Title 16 published on 2014-01-01
no entries appear in the Federal Register after this date.