I'm not sure who makes them, but my SR 3122 is an outstanding brush!FWIW, I find it very different from the Vulfix badger brush I owned. The SR is soft but without the floppiness of the Vulfix.
The numbers indicate the brush handle style and the knot size. For example, the venerable 3824 is a 38 style handle with a 24mm knot size.
The actual manufacturer of Savile Row brushes is debatable and somewhat irrelevant. I say irrelevant because Charles, of QED, has the brushes made to his specifications and he inspects the brushes to ensure they meet his standards/expectations. They ain't Savile Rows until Charles says they're Savile Rows![]()