The proper role for precious metals in investing is a great topic but too long for this comment.
Coin counting machines are great. Unfortunately, authentication of precious metal coins is an art form. A good forger can make gold plated lead coins that past most tests.
If you can find a group of people willing to barter coins; then go for it. I think it is fun to make transactions where the value of the transaction is a weight in precious metal.
The problem that people who want to create a large scale system of trading in coins face is that there are so many fake coins on the market that are bound to infiltrate and corrupt the system of barter.
People who were trading Pieces of Eight back in the 1700s had serious problems with the coins weighing different amounts and with coins and that had inconsistent amounts of precious metals.