Under the system I am working on now, you could own and trade with silver holdings only (or holdings for any other metal) at any divisible amount, as reckoned in fed dollars. That would be straight forward, and wouldn't have to be an ounce or a coin of any specific denomination. The merchant could still price everything in USD, and you would pay in exact equivalent USD using silver holdings (at fair market value for that day).
Another option, however, is a COMMODITY POOL, with diversified holdings that are far more stable in value (the more commodities there are, the more price stable the pool holdings).
HOW IT WORKS
Let's say you have 1 Troy ounce of silver, and want to add your silver into the local commodity pool.
Here's what an hypothetical pool looks like on the day you add your commodity:
Value Dist. % Gold
1715.20 $ 3.57 50.00 oz. 24000.00 gr $ 85,760 60.61% Silver
33.66 $ 0.07 500.00 oz. 240000.00 gr $ 16,830 11.89% Palladium
663.00 $ 1.38 30.00 oz. 14400.00 gr $ 19,890 14.06% Platinum
1607.00 $ 3.35 10.00 oz. 4800.00 gr $ 16,070 11.36% Aluminum
0.92 $ 0.0001319 2000.00 lbs. 14000000.00 gr $ 1,847 1.31% Copper
7.20 $ 0.0010286 100.00 lbs. 700000.00 gr $ 720 0.51% Nickel
7.67 $ 0.0010957 50.00 lbs. 350000.00 gr $ 384 0.27% TOTAL POOL:
$ 141,501 100.00%
That's the total pool. Holdings in that pool (for everyone) are based on their locked in percentage of ownership of the total value. That is physically allocated according to the value distribution of each commodity (far right column, total mass times the price of each).
Your silver is priced at USD $33.66 when you add it into the pool. Everyone in the pool agrees to trade the fair market value of your silver for the fair market value of a proportionate percentage of the entire pool. In other words, your one ounce of silver is buying into a lot of different metals, even as a lot of different metals are buying into your one ounce.
This zero-sum game exchange for everyone means that you no longer have one ounce of silver. You end up with the following:
Value Dist. Grains
₴ 20.40 5.7 gr 0.01 oz. Silver
₴ 4.01 57.2 gr 0.12 oz. Palladium ₴ 4.73 3.4 gr 0.01 oz. Platinum ₴ 3.82 1.1 gr 0.00 oz. Aluminum ₴ 0.44 3329.5 gr 0.48 lbs. Copper ₴ 0.17 166.5 gr 0.02 lbs. Nickel ₴ 0.09 83.2 gr 0.01 lbs. ₴ 33.66 TOTAL SHARE:
0.02378221% VALUE: ₴ 33.66
You now own holdings in gold, silver, palladium, platinum, aluminum, copper and nickel. Your share is now locked in (as a percentage of total pool value), and you are immediately diversified, as are all other holders.
(NOTE: I use the ₴ sign to distinguish holdings from their USD equivalent. It's called the hryvnia sign, and is used by the Ukraine for its currency. All computers have it, and Excel recognizes it as a currency symbol. I like it because it's basically a backwards S with an equal sign running through it)
PRICE OF SILVER FALLS
Now let's say that the price of silver falls to $30 the very next day, as you said. The value of your diversified holding would change to $33.22, not $30. On the upside it works the same way. Let's say that the price of silver (and only silver) changes, this time with an upward swing to $36. The market value of your holdings would only increase to $33.94.
So if you want to speculate, and put your trust in the one metal's performance over all others, stick with a single metal holding. If you want your holding to be more value stable through diversification, insulated and buffered from highs and the lows, you would participate in the pool.
Also note: one thing you cannot do is selectively pull out of a pool (i.e., you can't buy in with silver and extract gold). It's not a gaming and speculation tool, and you would not have the right or the power to "undiversify" everyone else in the pool. It's nothing more than a diversified store of value.
There's a lot more to it, of course, but that's partly it in a nutshell.
EDIT: One more thing. Let's say that you trade with a merchant using a SILVER ONLY holding. The merchant has the option of IMMEDIATELY converting that to a pooled commodity holding, to stabilize its value. But it's a one-way street. You can't convert from a pool to a single metal unless you have someone willing to trade their single metal holding for a pooled holding. That would be a separate exchange, external to the system.