I have Goodmans 2 Maxims. The first bought in early 1960's, (I would have thought 1963 but a comment above suggest it was not available until 1965) the second about 4 years later. The earlier one has a GOODMANS label on the front, teminal connections and 'Goodmans Industries' as the manufacturer on the back. The later one has a G Logo on the front, socket connection and 'Goodmans Loudspeakers Ltd' as the manufacturer.
I have always known that the earlier one is less sensitive than the later one, but when balanced with the amp they sound the same to my ears.
Now I come to try to sell them and check the weight for postage purposes I find that the older one weighs 3.9 kilos, the newer, 2.9 kilos, an huge difference.
Has anyone a plausible explanation for this? Alnico springs to mind, but surely suitable Alnico speakers would have been available by 1963 and a difference of a kilo in the weight of the speakers sounds improbable.
It would also be interesting to know which model was being used by the BBC for their comparisons.