[broadgage]

The "very large and expensive" battery to which I referred in post #37 was not a type 991 lantern battery.
I was familiar with 991 lantern batteries and still use the odd one.

The battery that I recall was much larger, and probably contained 4 flag cells. Too big to be portable.
A relative obtained a couple for lighting when other batteries were in short supply.

I have never seen these since, I do recall some pictures of an old Antarctic base that shows what looks like one of these on a shelf.