At $5 billion a year, the rare-coin market is so big that when the government lays claim to some marquee pieces in private hands, the decision makes national headlines.

The first $1 million pledge in the American Numismatic Association’s $40 million fund-raising effort to put museums on both coasts and improve the one in Colorado Springs, Colo., was made by Steven L. Contursi, president of Rare Coin Wholesalers of Dana Point, Calif.