At least since 1883 -
Sport with Gun and Rod in American Woods and Waters by Alfred Marshall Mayer
https://books.google.com/books?id=IJcCAAAAYAAJ&pg=PA781&vq The choke-bore now almost universally adopted by gunmakers is as follows: Taking a twelve-gauge gun as an example, the construction of the bore from the front of the breech-chamber to within one and a half inch of the muzzle amounts to about 1/100 of an inch. At one and a half inch from the muzzle begins a sharp contraction which, in the length of one inch, equals 25/1000 of an inch. The last half inch of the bore is a true cylinder.
.010" + .025" = .035" constriction = "choke bore"
That would be the 'taper bore' which was not commonly used by U.S. makers, but often used in advertising
![[Linked Image from photos.smugmug.com]](https://photos.smugmug.com/US-Makers/Lefever/i-CvBQDsN/0/29f235a1/L/Lefever%20boring%203-1916%20Forest%20%26%20Stream-L.png)
In the 1907 edition of Greener's
The Gun and Its Development .030" - .040” is Full or “Choke Bore”
https://books.google.com/books?id=3HMCAAAAYAAJ&pg=PA251With modern premium shells it is very likely to pattern the 'Full' standard of 70%