It was what I thought it was then. The gummer had an impeller inside of it I think. Must have had a drive shaft on the cutter that fitted into it. Anyway, I recall it being one heavy lump of metal if it was in your way!
where exactly did it fit on the cutters we are familiar with? like the one above (repeated below)
(I should say the museum has a mock coal seam which the jib disappears into, which is the black area on the right of the photo)