Cleaning Residue From A 1925 Penny

Hi guys,

You've probably seen the title and thought "no no no", but I would like some input on the devaluation of cleaning an Australian copper penny. My understanding has always been once you clean it, it's worth virtually nothing as the appeal disappears for the collector / the cleaning process damages the coin and as a result of this, I have never attempted to clean a coin. In this particular case it's one 1925 penny that I found in an old bag of mixed coins at a garage sale.

Now, I've always stuck to the philosophy of "Don't clean a coin... ever" especially If it's of any particular value. The coin I'm talking about, as you can see in the photos below, has a large buildup of green residue on the reverse and minimal amounts on the obverse. Other than the residue (which I'm not sure if technically classed as verdigris) the coin isn't in too bad shape.

At what point does a valuable coin become too dirty to be worth anything? One person has been continuously suggesting that I should attempt some form of cleaning as it they think it would be worth more after cleaning (without damaging the coin) than it would be with the green residue.

I also have another 1925 that is also in rough shape - I can post photos if anyone is interested.

Any input on this post is greatly appreciated.

Thanks,
Nik.