The computer panels were made by an external company, Space Models of Feltham, Middlesex. The same company made the Eagle models for Brian Johnson. They also made the Year 2 Command Center computers using the same design, so the two types of computer panels could be swapped.
Each computer panel is 2 feet (61cm) wide by 1 foot (30cm) tall, although there are actually two slightly different sizes. They are made of a wood or perspex rectangle with a wooden frame behind. The front is spray painted with grey, although the hardboard ones are hand painted.
The panels slot into the wall frame much as they are depicted on the series, although when it is done on screen, the wooden frame is painted white. The top and bottom of the back frame have cup hooks, which are used to hold the panels in place (see more back details)
The electronics behind the panels to make lights flash caused a mechanical clicking sound, unlike the computer hum added in post production sound editing.
This is a "blank" panel (normally at the bottom of any computer wall), and a faux "grille" panel, normally on the second row above. Notice these are slightly different sizes. Thanks to Simon Rhodes.
The blank panel is numbered 86 on the back; the grille is numbered 107 (or possibly 167).
The grille is painted on with a stencil (in year 2 they put real ventilation grilles on panels). A taller version of the grille stencil is used on the second top row, under the X5 computer panels, and also alongside the shorter version under the big screen.
Thanks to Simon Rhodes