Way to much corrosion. No not worth $20 in that grade. Not sure if it's a 1/2 penny or penny ? In either case these were minted in the many millions and would be considered a very common coin. I would have held out for a much better grade. IMHO.
Op, I am just asking. Are you newer to coin collecting, or at least collecting older coins? I ask that because it is a common misconception that older coins "should" be in lower grades, or corroded, etc. Let us be very clear, there is NEVER a reason a coin "should" be lower quality. Age does not matter. True, some coins are very rare NOT corroded or worn, but that has nothing to due with its date, and more to do to just history. All coins should be graded the same, like this one versus one struck yesterday. This coin is very available in nice condition. I just wanted to write this because WAY too many people think its ok for a coin to have damage "because it is almost 200 years old". In coin collecting, that is never an excuse. A 200 year old coin, (or a 2 year old one), MAY have issues, but that is not because its 200 years old, and anyone selling you a coin using that as an excuse is LYING to you. Now, $20 is not a ton. Its a cool thing to hold if you haven't had one before. I would chalk it up to tuition for a coin collecting lesson. I have paid much for for lessons unfortunately.
If this is a half penny, in better condition maybe $20 retail. In this shape $10 retail and could be gotten for less. $5 is probably fair.
if you are happy with it then that is all that matters, if not let it be a lesson, if the true value is $10 then that is a cheap lesson, in this hobby research is your biggest friend. For what it's worth, I think your coin is pretty cool!!