As Kiwirob said....
But, to help explain further.
Full Naval Standards.
For the UK usually = Def-Stans, NES's & BR's.
http://www.dstan.mod.uk
These are the rules that layout EXACTLY what materials have to be used, how much damage the equipment must be able to sustain & still function, the colour of the surface finish, warning notices & labels, down to SPECIFIC dimensions & components that must be used, sourced from particular manufacturers or using NATO Codified parts (
NSN's).
This means that the product has probably been battle proven or tested to destruction, been through various other testing procedures (
possibly including operability under certain climactic conditions), & design / construction has been fully ratified by the MoD.
Lloyd's rules while being stringent, don't go that far (
by a long way).
...When discussing Domestic equipment (light switches / sockets / back boxes), guess which one is at LEAST 5 times the cost of the other, & guess which one is about 3 times the cost of the one YOU can buy from your local store.
Oh to be a supplier of equipment to the Shipbuilding Industry....
SA