Our new coins (1 cent to 25 cent) including the penny are now made of nickel coated steel. If you check the penny it can be picked up with a magnet. It has been a few years now that they quit using nickel and copper for our current coins. With the penny there has been no copper in them since 1996. They went from copper to zinc and now steel.
Depending on the ground conditions a lot of these new zinc and steel coins are going to be junk. I have found quarters now that are starting to rust. Some zinc pennies have holes eaten right through. They will be like our old steel nickels that were used in the war years. If you find them now they are pretty much garbage can material. One dollar and two dollar coins are better metal content.
I find that on a nice sand beach I pick up everything. Easy to dig and keeps the area fairly clean
Good luck on you search