This helmet is part of a ‘standard diving dress,’ an early type of underwater exploration gear. The suit is made from heavy canvas or rubberised material with brass or copper fittings. It includes a helmet with a glass faceplate and an air supply hose connected to a surface pump.

This scan was taken in situ and so the body and back are not visible. 

The helmet has two main parts: the bonnet, which covers the diver’s head, and the corselet, which supports the helmet’s weight on the diver’s shoulders and seals tightly to the suit. A manual air pump provided air for the diver, who communicated with the surface team by tugging on the air hose. These suits were weighted to help divers walk on the seabed.

The idea of the diving suit dates back to 1511, with the first design shown in a book by Vegetius. In the 19th century, developments meant that diving suits could be used to help with underwater construction, salvage, and scientific research.