What is the value of a 1931 silver dollar from panama?

The U.S. did not strike any silver dollars in 1931 due to the Depression.  Is your coin from another country?  If the date is correct and it is a U.S. "Peace" design, my first guess would be that it is a counterfeit piece, most likely made in the Far East.  A lot of copies of dollar-size coins are being churned out there, many with laughable errors (wrong date, wrong design, etc.), along and some that are almost undetectably good.