Resources To Find Cleaned Coins

Great question. This is of no help, I know, but since I haven't mastered that art myself, I pretty much assume everything raw is cleaned until proven/convinced otherwise. I am learning from this forum though just by seeing what others think is cleaned and asking why if it's not obvious.

bigfredd has a good point.. I took some MS modern coins and cleanded them and looked at them
and some 64' Kennedy's / Roosies and cleaned them to see how cleaned sliver looked.

Although there are many posts and articles about how to detect a cleaned coin, it really is not always correct. Way back in the old days many, many coins were cleaned due to many reasons. One common one was if you worked in a place that was rather a dirty place, your coins, currency, clothing, etc all picked up that dirt. So many people did several things to clean the coins. Some actually washed them in soap and water. Some used a brush and harsh soaps which was a common soap way back when. Lava for example.
Of course if you were a coin collector as a kid and showed anyone your coins, the first thing they would say is those are really dirty, why don't you clean them. And most kids did just that.
The point of this all is many old coins were cleaned way back in the old days. Some people still clean coins to make them look newer. Some just want them to look pretty.
In many instances it is rather difficult to tell a cleaned coin if done a long time ago, now in circulation, found new dirt and you find it. Recently cleaned coins are sometimes obvious. Others are done carefully and really not easy to spot.
To sum it all up, if you study cleaning of coins enough, you'll find it easier to spot most but still never sure on others.
Meantime I'm back to my coin cleaning pots.