I dont have any proofs yet but is it possible that they can be put into regular circulation with other coins? Thanks, Andrew
Yes, it is possible to find a proof in circulation. I have seen Lincoln cents and Statehood quarter proofs. TC
With coins from 1968 forward, the majority of proofs were produced in San Francisco, and from 1975 on, they only produced proofs (with few exceptions), so coins from those dates with the S mint mark are likely to be proofs. Second, you can tell they are proofs by virtue of their mirrorlike surfaces. In circulation, these can become diminished, but they are still quite reflective and shiny.
Due to all the home, coin store and dealer robberies lately, you'll be finding a lot of proofs in change. Yes most will be noticed by the S mint mark but the older ones will just be lost due to wear, dents, scratches, etc. Robbers just dump thier coins in either those coin counting machines or take to a bank. Then from there, into circulation. After a while, they are just coins.