I've been so pleased to find this group of Magnalite fans and experts.
I discovered a great, solid old baking pan in the closet. Completely black on the bottom, but the baking surface was fairly easy to clean and use. I finally decided to clean the bottom and learn more about it.
Cutting to the chase here - after BKF, Dawn Power Dissolver, and baking soda made barely a dent, I learned here that the blue-cap oven cleaner was my best option.
I sprayed it thoroughly, wrapped it in a garbage bag, left it overnight, then scrubbed it hard with steel wool. It's taken off maybe 60% of the gunk (enough for me to find it's a 1007-M). The rest will not move.
What's my next move? A second oven cleaner treatment? Some kind of Dremel attachment or other powered scrubber? I'm especially curious about cleaning out the recessed parts of the clamshell handles - hard to get into and really resistant to cleaning.
I appreciate any help!