Neat family heirloom, but the 'F' indicates the lowest grade hammer gun. There is little market interest today for typically well used 12g utility grade doubles. So unless in very high condition, and assuming it is in usable condition (which a gunsmith would need to determine) it would sell at a gun shop for more than $500 and less than $1000.
You could check the internet auction sites like Guns International for a gun in similar condition, but the prices are asking, not actual selling.