Modern Pattern And Trial Coins

Mints are always experimenting to improve the coinage, or in response to new legislation.
In almost all cases, they destroy the products of experimentation.

In times past, a mint master may have kept one or two experimental coins for his own collection on privelege. However most modern mint practice dictates that all experimental coins are to be destroyed, due to their implied extremely high potential numismatic value.
That sort of privelege has long since been withdrawn from highly placed mint officials, due to the possibility of corruption.

That is why very modern experimental (or pattern) coins are so rarely seen on the numismatic market.

Curiously, very modern gross error coins are much more easily available to the collector.

There are some interesting $1 patterns given here:

http://www.smalldollars.com/index.html

There was an article posted here some time ago about experiments to bring the nickel production costs back under $0.05 each--in the article it was mentioned that the Mint wasted "several million" on experimental compositions, and the patterns were all destroyed and no action taken.

To my knowledge, there are extremely few modern patterns that are legal to own .