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The black spots are fine. These are "getter flashes", placed there to absorb stray gases inside the tubes. A silver or black appearance is normal. Any that have turned white are a sure sign of a bad tube.
If the set hasn't played in decades, it likely needs a bunch of capacitors replaced. A real thorough going-over before just turning it on is a good idea to prevent damaging parts like the flyback or power transformer.
At the very least, bring the power up slowly with a variac, or use a "dim bulb" type series lamp setup to limit current during initial testing.
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