It is beautiful, I don't believe the surfaces would warrant an uncirculated grade though. I would think AU58 but the grading services would probably consider it cleaned. Regardless it is a wonderful coin!
It's a nice find but it wouldn't get more than a "net" grade from ANACs and a genuine grade from PCGS. The coin shows "environmental damage" from its time in the ground and possibly from a cleaning. Value wise net grades earn about 50% of non-net grades.
Nice find! The bad news is that the 1858-O is one of the commonest dates in Seated halves, so the cleaning and surface porosity will hurt the value quite a bit. It had AU/Unc. details, and I would expect a final price of $40 to $80 if you were to sell it off in an Ebay auction. A certified, no-problem example of this coin in AU-55 could be purchased around $220. The reason the cleaning and porosity hurts the value so much is that collectors have many, many examples of this date from which to choose, so they can be fussy. Many people will not bid on a dug coin.
Hypoman:
No ignorance at all; only a thirst for knowledge; congrats!!
Porosity is the little pits which cause a sandpaper-like finish; surface granularity.
Shady sellers may cover the pits with epoxy or shoe polish.
Value takes a greater hit the greater the porosity.
Don.....