Unless you have factory documentation of the swivels being original, swivels will detract greatly from the market value of an American double. Last I knew the members of the PGCA have yet to put an existing Parker Bros. gun with swivels together with an order that calls for swivels. I have a 28-gauge Flues Grade 1S that had swivels on it when I got it but Turnbull removed them when I had the gun completely refurbished. The only reason I had the gun refurbished was that it had ultra rare 30-inch barrels. Flues Model 28-gauges were only catalogued with 24- and 26-inch barrels.
In that I've never seen an American double with factory documented swivels, I don't know what they would add to the market price.
