[paulsherwin]

My guess is it's part of a minicomputer terminal. Not all manufacturers supplied a £ keycap to replace the # one, and some terminals couldn't even display 0x23 as £ on the screen. This was much less important in the 70s than it would become later, as most terminals were used in scientific and higher education environments. Commercial systems for applications like accounts and payroll were usually supplied with highly nonstandard tailored keyboards.