IBM 5150 - Disk Cover Plate
IBM referred to this as the "DISK COVER PLATE". The IBM part number is 8529204. (Reference: IBM 5150 Hardware Maintenance and Service, AUG81, pages 4-4 and 4-5)
This web page exists because some people have expressed an interest in making their own equivalent.
Dimensions of the black plastic component of the plate are 150 mm x 86 mm x 5 mm (the 5 mm being the 'edge' as shown in photo #4 below)
Photo #1 - front
Photo #2 - rear
Photo #3 - disassembled
Photo #4 - edge