One thing is the neat looking vintage packaging shown in the advertisement, another and more intriguing thing is the cross sections. The “less honest” brush with the plug shows a way of using less hair in a brush of a given diameter that I’ve not even imagined before… I just assumed less dense brushes were simple less well packed.
Makes you wonder about the ‘glue plug’ one sometimes sees in cheap grocery store brushes over here… is it big because manufacture and quality control is sloppy, or to hide the fact that it’s a loosely packed brush?