kwc271, the photo of the gun mount you found at world.guns (link below) is the Type C16. The front sight actually clamps on to the barrel of the shotgun, and the aerial rear sight is attached to the gun cradle mount.

Jack, are you saying they actually modified the sights on the shotgun? I can't recall seeing one like that. But I haven't seen that many either.

Here's the link to the Type C16 photo: http://world.guns.ru/shotgun/remington_11_aerial.jpg