That must be a Very Powerfull Magnet. And I suspect that the steel coins will not last long in the ground or on a beach. And I doubt if I would ever find one as I usually ignore iron/steel signals.
But with USA nickel composed of 75% copper you would thing they would register higher than they do.
I am going to be doing some test to see where the 99.9% nickel coins show up on my detector