Variances in chokes?

[Austin W Hogan]

I remember several brief passages about methods of patterning including one which implied the old board had been replaced with a new 24 inch board. I would probably spend a week turning pages to reconstruct this.
The conclusion I have drawn is that the barrel department had a grid which was used to pattern. It was probably coated with whitewash between shots. The number of pellets in a sector were counted or estimated, and multiplied by a number to state a pattern.
Returning to the original question; has anyone found any pre 1920 cases?

Best, Austin