This case has MTA1279 (Midland Texas America, 12th week 1979) stamped on it. There is also a sticker on the back "NOTICE Sometimes your Speak&Spell will turn on in the "SAY IT" mode instead of the "SPELL A" mode. When this happens, you should press the # key and then the ON key again. Press GO to start the activity." It doesn't power up- no display or sound - I haven't tried to figure out why. I will try to dump the ROMs before decapping the chips. Another unit is on the way with broken buttons, so I was going to swap parts until I get a working one, then decap the other.
I hadn't read Gene Frantz' article until this weekend. Pretty interesting: http://cnx.org/contents/b3014cd9-6e3a-474f-bbaa-c948cbc8e205:1/The_Speak_N_Spell_