The famous GE 9x21" speaker! They used them in a couple sets, but normally only one of them, on the bottom. I have one such set. They left the back open in the speaker compartment so that you could show all your friends - "Wow! Look at that speaker!", - "Yeah, it's a 9x21 - the sound is as wide as the screen."
Interesting thing about those speakers, they have the exact same mounting holes as the 8 by 12. The 8x12 is also listed as an alternate part in the Sam's. GE used them for a while, then switched to the 9x21. They have pretty good sound, with the coaxially mounted tweeter. They're just weird looking.
That's what television these days is missing! Wide sound.
-Ian