This Barnes "Swan on Swan" slug iron was auctioned on May 1, 2016 and sold for the winning bid of $6,000.
Of special interest is that this is the original patent model. The attached note states it was found in the debris of the Patent Office fire of 1877.
The auction information and images are shared courtesy of William J. Jenack Auctioneers of Chester, New York. This auction was broadcast live on liveauctioneers.
See also Irons-Slug/Box Irons for another Barnes "Swan on Swan" Slug Iron.