The two Clauson mentioned above are "A William Clauson Concert" recorded in late 1957 (he was 27) at Town Hall in Wellington, NZ. It is record #T10158 on the 'Capitol of the World' series.The other, P8539, is "Stories in Song", no date. According to the liner notes he was born in Ohio, raised in Sweden, and was living in California at the time the record was produced. And he apparently was very popular in Mexico where he was called El Charro Guera.
Hope this adds to, or confirms, this discussion.