It looks very similar to the one on my 358 NM. It was made by the gunsmith who installed the barrel.
Mine has a solid bottom, so there's some muzzle flip control, but with the holes drilled at 90 degree angles, I can see no recoil reduction.
Your's seems to have holes all around, and drilled at 90 degree angles, so I can't see any real control at all. Holes should be angled to the rear for recoil reduction. YMMV
Harvey/ Ga