Trap hit it on the head...somebody putting dug coins back into circulation...just this weekend, at the convenient store, I didn't want to use my debit card to buy a newspaper, so I grabbed my pouch and my wire brush and gave some quarters a quick clean...got a funny look at first, but they know me and know what I do. ..Ddf
Yep, most clad Washington quarters that have been in the ground for a while are going to turn an orange / brown color.
Clad Quarters, (1965 to present ), are 75% copper and 25% nickel. These are nonferrous metals. Nonferrous metals don't rust.
I noticed this was your very first post arbrnirish - so, Welcome Aboard! You didn't list your state (or country) in your profile. So, you might consider jumping over to Sub-Forums: Select Your Area.... and selecting location information (i.e., clubs, hunts, finds, legends, maps, etc.) directly related to your state (or country).