During my paint selling days, I don't recall ever having a 5" paint brush. Sash and trim brushes came in 1 1/2", 2", 2 1/2" and 3" widths and were chiseled brushes, with the tips on a slant. Wall brushes came in 3", 4" and 6" widths, while exterior paint brushes came in 4" and 6" widths. Brushes were generally very expensive, with an open center, leather bound brush selling for about $150.
This post really brings back some memories!
Bob Wright