Hello, you're disc is too low, 6 to 6.8 is a good deal, when you've got the silencer at -1, don't forget that some irons will crack more than usual, but this is the only way to raise more and more the reactivity of the Deus in a ferrous spot. If your field game was full of litlle iron, maybe the TX3 was too high. The audio response at 7 (in my case) increase the small and deepest sounds of a litlle item, but it raises the false signals too, it's just an habit, but you should try 5 or 6.
When you project to search some antic coins, the metal detector has to be the most sensitive, so it could appears more unstable...but this is the key to success in this very specific case.
Forget the notch, when a target is closed of a ferrous, and specially a little coin like billon coins or silver, or if the soil is higly mineralized, the ID is drag to the low ID, so you need to dig everything, of course most of the time, good items are found beetween 30 to 98, but sometimes it does worth it. If you don't want to dig the small ID just look the ID on the RC screen and feel free to dig according you're desire.
It's difficult to explain everything accross a forum, not in my maternal language, it would have been better to help you side by side on the field, but, well, I will try to help as I can
See ya
PS : don't forget to put manually the silencer at -1 on reactivity 2 BUT don't forget that if the soil is full of ferrous pieces, like rusty nails, the reac should be at 3.