Generally speaking, the classic bat-wing double stitching seen on denim back pockets.
From a legal sense, however, the classic double stitched arctuates or arcs that have become so recognizable originated with the very first Levi’s jeans. Acknowledged as the world’s oldest clothing trademark, the shape became synonymous with Levi’s jeans by 1900.
In fact, the classic arcs are so closely associated with Levi’s that no other denim brand is allowed to sell denim in the U.S. with a similar pattern (read our previous article – “4 Years Later – Levis v.s. Japanese Repro Lawsuit Still Fair Game?“)
Levi’s back pocket arctuates (source: sura-la.com)
The arctuate making process:
Vintage Levi’s from 1930’s to 1960’s with some arctuate information: