How would you grade this? G4? VG8 details with surface corrosion? And, how much is it worth in this grade? NGC only charts VF on up: https://www.ngccoin.com/price-guide/world/ireland-1-2-penny-km-140-1775-1782-cuid-31489-duid-92753
On a related note - there are apparently some interesting contemporary counterfeits: http://irishcoins.com/?id=5449
If it's a regal issue and not a rare date or issue (I don't have my books handy), it's not worth much. Maybe $5 in a pick box. Too much porosity (corrosion?). Grading corroded coppers are difficult and I'll leave that to the large cent guys. A rough, inexperienced guess is VF details, net VG maybe.
