The display's plastic cover should be held snug to the LCD screen by metal tabs that go through little slots in the display's circuit board. If you take this plastic cover off (shouldn't ever need to do this, but it's possible your 60's previous owner did) and don't get enough pressure on the LCD when you reassemble, the display can look weird (lines out, completely blank, etc.). If you go in and tighten up the tabs, you might be able to fix your screen.
Your screen looks different than mine did, and my guess is that you're going to have to get a whole new display, but you could try tightening up the tabs to see if it helps before you spend a bunch of money. Just be careful that you don't break those tabs off or slam them against the circuit board and short it out.
12 bit...