There seems to be some confusion about the iron mask feature. Back when I owned the Original Sovereign years ago and Minelab was willing to help their customers this what Minelab related to me. They didn't go into enough detail to give away any secrets about how the iron mask feature worked but said that even without the iron mask feature the BBS technology still separated coins from iron reliably and that the iron mask feature under "some conditions" depending on mineralization and settings would improve the signal. They also said that with it off the BBS technology would still separate a coin and iron but under "some conditions" depending on mineralization and settings a coin next to iron could be lost. Turning the iron mask switch off switch does not stop the detector from separating ferrous from non-ferrous but turning it on can enhance the signal under "some conditions".