Hotpoint Dryer
Jeff, the reason for the clean out panel in the Hotpoint dryer is that both the LB, blower model and LC, condenser model shared the same basic inner perforated drum and solid outer tub construction. Because of that, lint would accumulate between the tubs. Sharing this design, the original design Hamilton dryers had cleanout ports in their drums and Frigidaire Filtrators gave some access for cleanout when the Filtrator cartridge was removed. Later, the Sheer Look Filtrators had a clean out port on the rear of the drum to help with this task. Some of the condenser washer-dryer combinations had panels in the inner basket that gave access to the outer tub so that the lint could be removed from thermostats and other places where it lodged.
If this lady saw the stuff behind that cleanout panel, she would probably think it was insulation, which it had become, but not in a good way. That's sort of like some owners of Maytag HOH dryers who thought that the lint buildup on the revolving Dynamic Disc lint filter was part of the filter and worried that a service person had removed and not replaced a vital part of the machine when he cleaned the mat from the filter.
That little plastic button at the top of the door was the mounting tab for a little plastic cage which held an air freshener tablet.