With it on you will have a better chance to pick up non ferrous targets that are close to ferrous ones. For coin hunting it means you will pick up a coin that is close to iron, but some big iron will also give a signal too, but with a little experience with the GT. you will be able to tell it is iron the way it acts.
I am detecting a farm site doing a field test on a coil and it has a lot of iron around like most all farm sites. I am hearing my nulling of iron,but listening to the other tones changing of other targets trying to hear those high pitched of a good coin. Now with the iron mask on I have a good chance to pick up a coin in with this iron and got a wheaties that was 7-8 inches down that I would not have if I had the iron mask off. After the wheaties was out of the hole the threshold just nulled. Got a few wheaties then get one of those nulls of iron, but can hear the tones trying to climb too in with the nulls and switch off the iron mask and it just nulled. I switch the iron mask back on and could hear the tones again, so i pinpointed and dug a plug, then went in with the Sun Ray S1 probe in all metal and picked out a wheatie then a big rusty nail, then a 1937 buffalo nickle, then more wheaties another nail then a silver Rosie and a 1941 nickle. Total was 2 nickles, a silver Rosie, 7 wheaties from 1916-1945 and 2 big rusty nails. If I had my iron mask off I would not have got a signal with the nails masking the coins. This is why I leave mine on on my GT. Those that have the XS, XS2, XS2a and the Elite iron mask is on all the time as it cannot be turned off.
Rick
I am detecting a farm site doing a field test on a coil and it has a lot of iron around like most all farm sites. I am hearing my nulling of iron,but listening to the other tones changing of other targets trying to hear those high pitched of a good coin. Now with the iron mask on I have a good chance to pick up a coin in with this iron and got a wheaties that was 7-8 inches down that I would not have if I had the iron mask off. After the wheaties was out of the hole the threshold just nulled. Got a few wheaties then get one of those nulls of iron, but can hear the tones trying to climb too in with the nulls and switch off the iron mask and it just nulled. I switch the iron mask back on and could hear the tones again, so i pinpointed and dug a plug, then went in with the Sun Ray S1 probe in all metal and picked out a wheatie then a big rusty nail, then a 1937 buffalo nickle, then more wheaties another nail then a silver Rosie and a 1941 nickle. Total was 2 nickles, a silver Rosie, 7 wheaties from 1916-1945 and 2 big rusty nails. If I had my iron mask off I would not have got a signal with the nails masking the coins. This is why I leave mine on on my GT. Those that have the XS, XS2, XS2a and the Elite iron mask is on all the time as it cannot be turned off.
Rick