Mark Levinson - how to fix white logo paint that has peeled away?

If it is a water based paint you could also quickly wipe off any that strayed outside of the trough.

Or, and I know this is going to sound weird, but find a guy who collects and paints miniature soldiers. I have a friend who does this and what he can do with a paint brush is unbelievable.

Even if you found the right white, the paint on the amp would probably discolored after all of these years. It would likely be unnoticeable though. Just put the thin paint in the trough carefully with a pin as another said. 

I used to sell and mix custom paint colors and there are a thousand different shades of white.  Each one had little bits of yellow, black, red...
Whatever it took to get the desired shade.  You will never match it exactly without knowing the precise paint code.  That said, I would leave it alone.  Just tell people you have a Mark Levinsor amplifier.  

What rockness said and use these or similar.
http://www.automotivetouchup.com/store/accessories/micro_dabbers.aspx

Yes, if you plan to do it yourself call ML and get the exact paint color. White is very hard to match and even slightly off will look worse than it is now IMO.

Levinson used General Motors paint I was once told by one of their company reps.  I don't recall the exact name of the white, but he said that it was the purest white paint that they had found at that time.  Call Levinson and ask!

There are paint sticks such as this that are designed specifically for filling in engraved lettering or lines.

I think that I would try getting some paint that I could thin out enough so that it runs a bit, then set the amp so that the face is horizontal with the ground and dab it in with a something a bit smaller then the groove (pin/needle).

Are the letters grooved into the front of the unit?