The Thos Parker (nice wood!) muzzleloader is probably a Belgian import: http://www.shotgunworld.com/bbs/viewtopic.php?t=305806
"Essex Gun Works" was one of several hundred brands manufactured by Crescent Firearms of Norwich, CT:
http://www.shotgunworld.com/bbs/viewtopic.php?t=364601...
In today's market, $200-400 would be good for a functioning BP shotgun with sound barrels, unless it's a "collectible" maker or in extraordinarily fine condition. The front action locks are generally more valuable, especially if they hold both half and full cocked positions symmetrically. A...