Found this article about the Roelof Twenty hat from Printer's Ink March 23, 1911! Possibly the first time a "Twenty" was advertised. They say in the article that the "hat" was made for special customers for four years.
The first Knox Twenty was from 1915 as seen in this thread on the Knox Forty, Thirty, and Twenty. KnoxReference
B
The first Knox Twenty was from 1915 as seen in this thread on the Knox Forty, Thirty, and Twenty. KnoxReference
B