The porthole glass on boats must be of toughened glass and marked to the relavent British Standard.
Usually this results in a "kite mark" visible on the face of the glass.
These glasses were supplied by Midland Industrial Glass and have been marked with the BSEN , not where it will be seen, but on or close to the glass rim where it will be hidden when installed. I have therfore photographed the glasses and obtained paperwork to prove their origin in future.
Here the glass has been stuck in place in the brass porthole with silicone sealant.
A gasket made of closed cell rubber window tap is then attached. The join is at the bottom of course.
The porthole is then bolted to the cabin although it will be removed for shot blasting.
This view shows the inside, painted to protect the steel against condensation although the wooden cabin porthole liner will be sealed against the glass with silicone sealant.