I'm not sure how many times I have read that Somerset (Nimmer Mills/Carter-era) brushes are characterised by the use of "surface" lamp-black, rather than etching, hammering/stamping, but that's not absolutely correct. I have several earlier Somerset brushes (Nimmer Mills butterscotch) that are a combination of these processes. Below is a Case in Best that is such a brush. The letter stamping tool was first held over a lamp flame to gather the soot or "lamp black" and the lettering was then stamped into the handle.
From what I can tell, Carter-era brushes (the later Carter period, using the very white material) have ONLY "surface" lamp black. I don't know how it was applied. Vulfix brushes are characterised by automated, etched lettering.
Below is the Case, mentioned above: