IBM 1800409-001A - Manual (Page 284)

2. Using a Phillips screwdriver, remove the two screws from the
blank optional I/O plate, and then remove the plate from the
interface panel and set it aside (fig. 8.17).
Fig. 8.17 Remove the Optional I/O Plate
Chapter 8
8 - 2 8 P r i n t e r O p t i o n s