Bottom is Small Swivel 
Bottom right is Small Swivel
This is an excellent reproduction of a Rail Gun 1” bore cast on a 77,000 PSI high pressure tube, with cast tiller supplied with a yoke and support. This is suitable for fortress mounting or in a small boat. As it is shown here with our post system for field use. We also have mounting systems available for Bateau or Gun Boats. We offer a full range of tools and accessories for F and I, Rev War and 1812 periods to complete your impression.