The style of the side window grills on this helmet matches those on early A.Siebe helmets. This helmet is however repaired many times, it must have spent decades under water. Never saw one exactly like it and can not confirm its identity, my best guess is that at some stage a helmet was repaired with either genuine A.Siebe parts or an A.Siebe helmet was repaired with other parts. Considering its age it still is a rare find. Price on request.
Early Diving Helmet. A.Siebe(?)