Some Finds From The Good Old Days Of Metal Detecting.

[GB_Amateur]

1 hour ago, fogrider said:

I dug a Victorian English penny a month ago, and it was beautiful (It's the one I use for my profile picture). Likely been in the ground for 80+ years.

Seems like copper and tin make a stable combination.

Since you dig Canadian coins, here's a datapoint for you, and a question.  I have a mid-teens Canadian large cent which I found in an old schoolyard near where a large tree had been removed.  (I've noticed that the chemicals in some decaying tree leaves can be really hard on some coins, particularly our 25% Ni, 75% Cu coins -- our 5 cent pieces and clad.)  This large cent has a lot of crusty buildup, seemingly worse than our Lincoln cents of the same time period.  Do you know the composition of those 19-teens large cents?

[fogrider]

2 hours ago, GB_Amateur said:

Since you dig Canadian coins, here's a datapoint for you, and a question.  I have a mid-teens Canadian large cent which I found in an old schoolyard near where a large tree had been removed.  (I've noticed that the chemicals in some decaying tree leaves can be really hard on some coins, particularly our 25% Ni, 75% Cu coins -- our 5 cent pieces and clad.)  This large cent has a lot of crusty buildup, seemingly worse than our Lincoln cents of the same time period.  Do you know the composition of those 19-teens large cents?

95.5% copper, 3% tin, 1.5% zinc. So, basically a bronze alloy.

That might explain why the older "copper" Canadian pennies seem to last fairly well in the ground.

Here's how I clean old pennies:

1. Hot soapy water and a tooth brush. Then:

2. A 5:1 mix of water and CLR with a tooth brush until the gunk is gone. Don't soak the penny in the water/CLR mix, as the metal may etch. The crusty build-up usually disappears.

3. Nasty black crud can be removed with a wooden toothpick dipped in the water/CLR solution.

I try to leave some patina on the coins.

[GB_Amateur]

3 hours ago, GB_Amateur said:

I have a mid-teens Canadian large cent which I found in an old schoolyard near where a large tree had been removed.

26 minutes ago, fogrider said:

95.5% copper, 3% tin, 1.5% zinc. So, basically a bronze alloy.

Here's a photo, from left to right:  two Indian Head Cents, the 1917 Canadian Large Cent, a modern brass USA dollar, and a 25% Ni, 75% Cu (surface layer alloy composition) clad Kennedy half dollar.

 

The (removed) tree that the cent was found under may have had additional deleterious effects on the coin, more than just the typical local soil.  The surface of that coin would serve as a pretty good fingernail file.  😏

[fogrider]

1 hour ago, GB_Amateur said:

The surface of that coin would serve as a pretty good fingernail file.

Try the water/CLR and toothbrush method on that Canadian large cent. You might have to work on it for several minutes. You might be pleasantly surprised.

The rust might be from an iron object that was near the coin. Typically, the old pennies don't rust.

I'm curious to see how it cleans up.....