Siebe Gorman 'Continental' Pattern diving helmet.
Copied by Siebe Gorman from the original Denayrouze design 3 bolt helmet. This 3 bolt design was a very successfull diving helmet on the European market, where it was built for the french, german and russian navies, as well as for many commercial enterprises.
Like the french 'lock' helmet, the danish 2 bolt helmet and several other designs which were not invented by Siebe Gorman, this 3 bolt helmet was not made in large quantities, it was rather an attempt from Siebe Gorman to monopolise the diving equipment market by offering every existing helmet in their sales catalogs.
This 'Continental' pattern helmet was offered for sale by Siebe Gorman from 1910 to 1970 aprox.