[Lynn Eades]

Hi Ron, This is the Jack used on British MkI carriers (mechanical screw type)
They used the bracket which was made to suit them. The Canadian jacking block evolved to fit their adopted hydraulic jack into the original mechanical jack bracket. That is how I see the evolution of it anyhow.

These are (were) made by various manufacturers. This one is Ern Lake. I also have a Britool one. Some are steel bodied, this one is alloy with a chequer plate base. They are variously dated
They are rated at 4 ton and 4 1/2 ton. there is an extension that clips on the top (I need one)
They come with a handle, and a two piece extension (fairly crude) I believe the early carriers had a longer single piece extension (which made it shorter than the two piece if you follow)
They lift higher than you might first think, and yes, it could be the same as the 4 tonner? (truck?)
There are different shaped ones as well.