Hi Tom,
You are right with your recollections...
I got a tip from 2 members in a Facebook Group as well.
You use a screwdriver shank that is a big and thick and place between the two silver tabs (in my red box in the photo) and turn the screwdriver down and towards you about a 90-degree rotation to unlock the latch on that side and then the same on the other side. Then the metal cover slides nicely towards the back and off the machine.
I thought I cleaned the machine well enough...but with this last cover off, I have decades of gunk to still work on...
.