In a surprise development in a high-stakes fight between Delaware and 30 other states, a special master has changed his recommendation to the U.S. Supreme Court, effectively urging a potential multimillion-dollar victory for Delaware.

The Supreme Court heard arguments on Oct. 3 in two cases, Delaware v. Pennsylvania and New Jersey, which was consolidated with Arkansas v. Delaware, on which state should get unclaimed MoneyGram “official checks” worth potentially $300 million to $500 million. The disputed financial instruments are MoneyGram “agent checks” and “teller’s checks,” which are sold only by financial institutions, and generally for large amounts.