Analog meter help

i have This detector. It has an analog meter. I was practicing outside with a penny,nickel,dime and quarter. The penny, dime, and quarter all maxed our the meter at over 10, while the nickel was between 6 and 7. I am sure its probably because the type of metal they are made with but just want to double check that it is common for newer coins to hit like that.

Thanks for the help