I was mystified when I saw this, too. But your question prompted me to look at my catalog stash and sure enough in 1969 the Solarus and Sonaro combo units were split into head-cab combinations. (Each was still a one-piece combo in 1968.) "Highly desirable for club and recording work, Solarus' total sound is achieved by combining state-of-the-art circuitry with two superb Sunn Guitar Transducers in an open back cabinet." The Solarus cab, 24w by 29h by 11.5d, had two 12" "heavy duty Sunn Guitar Transducers with heat treated voice coils."
And that sure does look like duct tape on those speakers!
Carter