Fee disputes don’t usually merit an appeal to a federal circuit court. Sums less than $100,000 would seem to be negotiable for a law firm with 2009 revenues of $705 million. But barring a late settlement, Winston & Strawn will square off against former client Doley Securities Inc. in the U.S. Court of Appeals for the D.C. Circuit next month over an unpaid bill of $84,412.19.

The case rests on an engagement letter, signed by Doley Securities in 2007, that stated an hourly rate for Winston partner Thomas Buchanan and ranges of rates for other lawyers, should they need to be brought in. Buchanan, who chairs the firm’s litigation practice in Washington, said the engagement letter was “almost identical to the ones every law firm everywhere gives to every client.”