Minelab Manticore questions

[DiggingSicilia]

I just got a manticore 2 weeks ago and finally took it out last Friday. I found two coins, which wasn't too bad for the large in the middle of nowhere farm. I got home and decided to test all the coins I had previously found with my Equinox 800. Out of 48 coins, 4 did not give the results I expected. My 1909 10 centesimi, 1920 20 centesimi, 50 lira, and 1982 500 lira came in around 28 but all the way at the top of the display and red line under the number. The first two I didn't think contained acmonital but apparently they do. I tested all 4 with a magnet and they are definitely ferrous.

I'm searching for other Italian manticore users to see if they have any experience with narrowing in on these coins.