Hey, you guys can bust my balls all you want, but get the facts straight first...

RayB, a small strip of molding around the corner doesn't quality as "T-molding on the back". A lot of the part with molding on the rear corner is on the "tab" that sticks up above the top of the game, so it could be considered the "top of the game". Not to mention, most Midway's I've seen have maybe 3-4" of molding there, not 8"... 8?!?
Fozzy, your Defender has T-molding all the way down the back? Wow, only one I've ever heard of, out of dozens I've seen... guess you just have that one "special" cabinet.

I'll forgive you though if you double check and realize you're wrong.
Secondly, Sure there were MDF cabinets in the early 80's. Most Galagas were MDF, most Gottliebs (Q*bert), Taitos, etc.
You guys seriously need to do some homework if you want to try to bust me on this stuff.

And PatrickL, no need to jump on the bandwagon, as obviously this wagon needs stronger wheels...

TTYL,
Wade
I'll correct you Wade:
Midways have the t-molding wrapping around the top back, about 8 inches down and then it stops. ;-)
Atari cabs tend to have molding along every edge available.
Actually, I'll correct him even further... My original defender cab has T-molding all the way down the back. They weren't all built in the same place at the same time. And another quick correction Wade... There are no MDF cabs from the early eighties, they're all plywood or chipboard (particle board), because there was no actual MDF in the early eighties. 
Best Regards,
Julian (Fozzy The Bear)