Is It Worth Trying To Save This 53 Halfpenny?

Very odd. Perhaps a Magicians coin (i.e hollow) or some sort of proof. My catalogue lists only 1 1853 coin issued to circulate and it was an overdate (3 over 2). The only other coin issued was a proof, known only in UNC.

However, Clayton does list an 1853 for about £5 in this condition. No word on its thickness.

The normal weight range given in Peck is 140.2 - 148.9grains. That's about 9.65grams at the top end. Depending on whether 9.5/6 means 9 and 5 sixths or 9.5 to 9.6 grams it is slightly overweight or just under the top value respectively. However, the amount of crud seen could easily amount to 0.2g. The weight limits are not set in stone. The normal thickness is 2 - 2.25mm with the proofs slightly thicker on occasion. FWIW, my 1839 proofs are all 2.35mm and the 1853 is 2.5mm thick. It is highly unlikely that a proof would get into circulation given the limited output and then get lost as well. 1853 is a much rarer date for the proofs than 1839.

The rims are not those of a proof, and even if it started out life as one, its present condition would make this irrelevant. 1853 is one of the commonest dates along with 1838, 1841, 1854, 1855 and 1858, so personally I would get rid of it and find a decent one as the coin is nothing like uncirculated. I'd give it around the VF mark allowing for the corrosion. You have lost the shield detail in parts and the hair strands are quite flat.

The 3 over 2 is only known from a couple dies and is genuinely scarce in UNC.

darge, it's late here and I'm tired but, as far as I remember acetone has little effect on copper/bronze or verdegris.

Long, long soak in acid free olive oil. Here we are talking months and then try to dislodge the verdigris with the softened end of a wooden toothpick.
It's good practice for when you have to do it on that really special coin you're maybe going to save one day.

I haven't found that acetone removes fingerprints - it seems to have no effect on them - perhaps I'm, not leaving it long enough. Do you leave the coin in the acetone ?

If so, for how long ?

How do you do it without the acetone evaporating ?

I haven't had success using acetone on copper coins, it seems to leave them looking unnatural.

Acetone will remove most organic compounds and any polar substances. Verdegris wont be affected unless you take advantage of some other chemistry - in light, Acetone photocatlyses with copper to Acetic Acid, which gives it some cleaning power. Negative effects to patina? I have no idea. But it will remove stuff quicker and start to eat away at verdegris (and patina, I suspect).

For an easier job, use BadThad's Verdicare. It removes verdegris and dirt and leaves a protective layer and it actually works.