Time Handling Vs. Grade

I've wondered the same thing.
If a circulating gold coin, the 'hands' were most likely washed, but if a copper
or a low face value silver coin the hands would have belonged to manual laborers.
Traces of coal dust, machine oil, street dirt and who knows what would be
imparted to the surface of coins.
Often members have suggested that a 'cleaned' or otherwise
mistreated coin be used as a pocket piece to lower the grade
but restore a natural surface.
Does anyone have definitive data?

The question that I have is:
"What mechanical process could be used to best duplicate
natural circulation?"

I believe there was previous thread discussing using a rock tumbler for this purpose.

SHAFTA9a raises the question:
"Were certain dates removed from circulation for a reason?"
Assume: The first and last dates of a series were removed, not only by collectors,
but by the non-collecting population as well.
If human nature is the same on both sides of border, the last decade of Canadian Large cents corresponds to the last decade of US Indian Head cents. More exist in higher grades, as well as lower grades, than previous years.

But the question remains, how long does unrestricted circulation take to make an EF coin a VG coin?

bpoc1,
I suggest that without a scientific test the only answer would be speculation.
Non-scientifically, the answer can only be speculation.
One reasonable 'guess' is this:
I collect the Barber series (1892-1916) which consist of dimes and quarters and halves. It is common knowledge that the condition of surviving examples is roughly in proportion to the purchasing power or each. A dime may lay forgotten in a house but a half? It was real money!
In 1920, and later during the Great Depression of the 1930s,
coins were spent. And spent.
Today, coins are dropped into a jar and brought to a bank to be dropped into a counting machine.
If a definitive answer is not to be had then all we can do
is speculate.
But I'd really like someone to come forward with an answer.

Scientifically, you might evaluate all the circumstances involved in circulation that involve wear on a coin, and then attempt to duplicate that in a controlled environment. If the original question is "the time it takes for a coin to get into such state", you would have to establish some parameters on how much time a coin in the real world experiences those wear conditions versus what you do to it in the lab, then extrapolate.

Conceivably you could come up with some kind of "standard" for "the time it takes" under normal circulating conditions for various grades, but, just thinking out loud, it would be so wildly variable in the real world as to become meaningless. As mathewvincent says, it depends on the denomination and the economic conditions at various times - how do you account for that? Look at the conditional rarity of 1930s era nickels in Canada. Today, the coins I receive don't circulate much - the times I spend cash, the change comes home and sits in a jar for a year or two, then goes to the bank and gets converted to bills. In modern Canada, perhaps look to the dollar and two dollar coins for real world circulation?

It's a timely topic, because in the past month here in the US I got a 1964 silver quarter in change. It was barely circulated. Obviously it sat somewhere for a long time, then somehow re-entered circulation. Only a week or two later, I got a 1965 clad quarter in change. That one has been spent constantly for 50 years. So many variables in this equation...

you're right, I was too general with the topic :S

But now I feel like experimenting. Once I get a nice new 2015 quarter in my change, i'll keep it as a pocket piece and see how far I can take it. If I remember, i'll try and post pictures