What this cover does on the FFC assembly
The 5031505009 is a Type Cover — a protective jacket that snaps over the back of a mated FFC plug, shielding the contact area and providing strain relief for the flex cable exit. It is not a contact-bearing connector; its sole job is mechanical retention and cable management on the 50-position assembly. This cover is designed for the 501786 and 501864 series FFC plugs, fitting the plug body after the FFC is inserted and latched. The 50-position count matches the plug's circuit count.