A luminous William Bradford oil depicting a whaleship off New Bedford (est. $60,000-$80,000) is among the highlights in Skinner's March 7 Americana auction. Also of note is an elegant Simon Willard tall clock in a classic Roxbury case (est. $30,000-$50,000), an enormous collection of mocha pottery (estimates range from $200 to $1,200), and a rare pair of polychrome fire buckets ($4,000-$6,000).