That is a great and simple tool. I have a very strong, some may say crazy, interest in the original tool. I have been making and selling the tools below for several years.
(https://i.ibb.co/VVRy6ZK/20230505-130949.jpg) (https://ibb.co/G7ywmLh)
(https://i.ibb.co/DM6P5mm/20230505-130900.jpg) (https://ibb.co/hdnxDrr)
The one without the handle is the (Williamsburg Master gunsmith) Richard Sulllivan model intended for use in a vise. Richard owns two like this. I have made these tools and sold probably 40-50 here on this forum and at the annual CLA shows for the last few years. They are not easy or quick to produce in my manual machine basement workshop. I also make the involute gears which are drilled and tapped for set screws. I have no current plans for making any more it just isn't worth the effort for what I can charge for them. I'm certainly not trying to sell them here, but I thought I would show what I believe to be the only ones perhaps ever produced in any numbers in the last couple hundred years. Several people have built one or two and they know it isn't easy. Ron Scott got me interested in this tool many years ago and I took up the challenge of developing it with the above two examples capable of working comfortably in 45 caliber and larger barrels.