Probably around 1971 - 1972, a new form of cab appeared - the "Companion" - more or less identical in form to the late Supreme cabs, but closed back and therefore considerably heavier.
The baffles still have cut-outs for the horns, but the openings were blanked off at the factory. Mounting harding was provided on top for fixing the Supreme amp.
Drivers were normally Celestion T1925 - a type of G12H Greenback with a whizzer cone. These were "all-purpose" drivers, perhaps better though for organ and bass than guitar.
The closed backs of these cabs - heavy slabs of 3/4" thick birch ply - adds to the bass response.
All-purpose "Companion" cab from 1972
One original driver - Celestion T1925 - remains with code HE = August 1972. Note that the heavy back has a chamfered edge and protrudes beyond the sides of the cab. The baffle has cut-outs for Midax horns but they were blanked off at the factory.
A pair of cabs with Eagle International tweeters added, and the opening for the upper Midax horns blanked off externally with a rectangle of aluminium. Speakers are Celestion T1925s. Note the consecutive serial numbers of the cabs: 122 and 123.