The guns are "Swan" guns. Marked "Utreck" on the locks. Ca. 1680. They are described in the text as being cheaply made guns. I don't think any of them have buttplates. The two on the right have rear sights, while the first one appears to have a dovetail for one. The first two forestocks are broken off. The barrels are about 2500mm (whatever that is in real measurements), and about 16.5mm caliber. These three guns are actually marked (stamped on the butt) 16, 17, and 18, and are believed to have been used in the great royal swan shoots. This book (Dutch Firearms by Arne Hoff) also states how that Dutch emigres headed for America were advised to bring guns such as these with them, as they would be needed in their new homes.