Welcome! My guess is a piece of aluminum allow. They are usually left after construction welding works. I found many of them in places with aluminum tube constrictions like tot lots, beaches, etc. Happy Hunting
Welcome from Maryland. Guess we should ask is it heavy? If it's lightweight then like others I say aluminum if heavy could be zinc mixture solder which I found pounds of.
You went with a gold digger? You'd better get rid of her quick and don't sign any insurance policies! Seriously,that's a blob of aluminum,as stated earlier. If I were to give a beginner advice I would tell them to dig mostly higher conductors to start,and the signal has to be solid,repeatable and not jump around,if you have a screen readout. That is so a person doesn't get disgusted digging up stuff like that. However,some stuff like that DOES read high and stable,so you're going to get some of that. Keep on looking,it gets a lot easier to tell you've got something good with time(and the same machine).