My yard is full of junk metal. I've got .68 acre and I'm not even 1/3 of the way cleaned of the nails and other junk. I've cleaned a 10'x10' area of iron and found a 1/2 crotal bell. I swung over that bell 100 times and never found it till the iron above it was cleared. Even discriminating out the iron. Everywhere I swing I hear iron. Thae area where I found the items pictured was a 4'x4' spot. Before clearing the iron, the mid and high tones always turn out to disappear once I break the soil. I figure cutting and removing the plug breaks the halo around the iron. Those items always turn out to be nails. Fortunately, I don't mind digging the junk.
Metal detecting is like a box of chocolates, you never know what you're going to get. I've only been doing this for 9 months and still learning every day.