My general rule when I was still actively detecting is that modern sites produce modern junk. In other words, you are going to need to detect in the right places if you want to find older items. You'll still find plenty of square nails, though. Trust me on that one. One good way to get started is to obtain permission to detect on sites which have been populated for a long time such as 18th and 19th century farms, homesteads, etc. if there are any in your area. Same thing with old churches. A particularly good time to detect is after fields are freshly plowed and the earth has been turned over.
Always obtain the owner's permission and remember to properly repair any landscape you dig up.
You can also detect on public lands where not forbidden by law. A couple of good sources there are places such as old schoolyards, playgrounds, boardwalks, traveling carnival sites, etc. where a lot of change fell out of pockets. Another good place to detect is if you live near towns/cities that have been established for a long time, especially when they are doing construction projects such as tearing up roads and sidewalks to replace them. Beach detecting can also be fun if you happen to be near the water as long as black sand is not an issue for your detector.
It's a little rougher here in Texas -- most of the land in the northern part of the state where I live wasn't settled prior to the middle of the 19th century, compared to, e.g. New York, New England, the Atlantic Coast, or Florida, where you can find coins and relics from the 1600s and 1700s. So a typical playground hunt for me might turn up a couple of bucks in modern pocket change or a few Wheat pennies if I got lucky. I have to go further out in the country if I want to find anything other than junk.
But even old sites are far from a guarantee. I still remember stopping on a road trip and detecting on the grounds of the old Salado Stagecoach Inn long before it was shuttered, and the adjacent land, and spending 4 or 5 hours pulling pop tabs, square nails, a couple of very rusty buttons, a few modern coins, and a horse bridle buckle or something to that effect.
I used to read all of the detector/prospector magazines like W&ET, CMJ, etc. and read these stories of folks pulling handfuls of silver coins and early copper, or gold and silver nuggets, and didn't realize until I got older that the articles were leaving out the days or weeks of "dry holes" and disappointment so they could highlight only the good finds from a particular trip. Of course, modern detectors have improved tremendously in 20-30 years. I still see stories all the time of going out with a modern rig and "re-hunting" sites that were long considered to be "hunted out" and pulling silver out of the ground that the old detectors couldn't pick up.
Good luck if you go coinshooting in the future, it's a great way to spend time with your kid and get out from the house.
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