Lightning LSJ query

I have a Mk9 lifejacket but it’s not the normal one you’d expect to see.

The LSJ is grey and the beaded handle is bright red. There’s only one pocket.

Anyone have any details on this?

It’s dated 1966, I’d like to know when it came into service, when it went out of service and what went in the pocket.

Hendon don’t have anything.

Thanks in advance, hopefully.