Not familiar with shovel history, but it's definitely not a design I've seen anytime recently. Still, here's a pic that MariposaGold posted back in February that somewhat resembles your find. That find was on the West Coast, and the Dahlonega gold-rush pre-dates the California event.
Is there still some wood in the socket of the shovel, can you post a photo of the back to see how it was formed?
I ask the question above because it just doesn't look old enough to be from the 1800s during the gold diggings in Ga., I hope it is but check out this topic which has a shovel that does look to be a gold rush era shovel.
Edit: I just notice that Mirage83 mentions this shovel below being posted in February, I sure the shovel your son found was used to dig for gold, it maybe as old as the Depression era when prospectors and a lot of other people when out to find a little gold to live from day to day.
Here are three additional pictures. It doesn't share that same reinforced assembly where the handle meets the blade. Just one additional rivet in the head/blade of the shovel. Mine seems to be a simpler design. Has metal running along top of handle and along the bottom with wood exposed from side view.
It's for sure an old shovel at least early 1900 up to the 20 or 30, and possibly late 1800s, I don't see the same type of common construction for it being early to mid 1800s, but it a keeper for sure, clean it up put little bee's wax to preserve it and make a wall hanging out of it!!