The design of U.S. coins has been staticfor at least a quarter-century, but Congress may be on the verge of authorizing new designs and picking up extra revenue in the process.

A new quarter, bearing a design on the tail side that commemorates the bicentennial of the Constitution, could be in circulation as early as 1991 if the legislation is approved.New half-dollar coins, nickels, dimes and pennies would be phased in over the next six years under the plan now under consideration.

There is widespread support in both the House and Senate for new coins, and authorization for the change is contained in a half-dozen bills. The biggest obstacle is time as Congress pushes toward adjournment, but supporters are confident of success this year.

In addition to delighting coin collectors, new coin designs would bring in as much as $1 billion for the U.S. Treasury, officials told Congress.

The profit results in part from the difference between the face value of coins and the costs of making them. It costs the U.S. Mint just 2.5 cents to produce a quarter, but the coin is then sold to the Federal Reserve for 25 cents.

Additional profit results from the fact that millions of coins would become souvenirs and be taken out of circulation.

U.S. coins have been changed 33 times in the nation's history, but not recently. The tail sides of the quarter and half dollar were last changed in 1976. The dime was changed in 1946, the nickel in 1938 and the penny in 1959.

"The United States has dragged behind other nations in coin design. There's no reason other than the inertia, the reluctance to change," says Rep. Henry Gonzalez, D-Texas, chairman of the House Banking, Finance and Urban Affairs Committee. "It's overdue. Coin design is something that should have happened a long time ago."

The proposed redesigns would only affect the tails of the five coins. The heads would continue to bear the images of past presidents - Lincoln, Jefferson, Franklin Roosevelt, Washington and Kennedy - but would be modernized. In addition, all present inscriptions, such as "In God We Trust," and "E Pluribus Unum" would remain.