Over forty of the world's leading software houses have one thing in common - Transam Microsystems

It's another advert from Transam Microsystems Limited, showing a generic Transam box, that might be a Tuscan, in the "PET on steroids" style that Transam seemed to like, together with a scattering of 8" and 5.25" floppies. 

The advert is not for any particular box, but for Transam's software division - TCL Software - which seemed to be churning out a lot of CP/M stuff. 

CP/M was the operating system that MS-DOS was, er, "based" on. MS-DOS was the operating system that was irrevocably tied to the fortunes of the IBM PC - launched a year before - and which would soon completely sideline CP/M, as well as pretty much everything else.