Also known as Checkering, this detail is on one of the handles on barrow Ruination.
Mr Geoff Slee down in Bacchus Marsh was kind enough to show me the tools and techniques involved.
I purchased from Brownells in the U.S the VE60 Cutter and the SD20 Cutter Gunline Tools. Unfortunately the handle was on back-order. I persisted however and eventually could not feel my thumb, index or middle finger. Surprisingly I found I had great control.
The cutters work on a scraping cut which require 5 to 6 passes for each run.