To start, it's roughly 40 years old, more or less.
If a dog ages seven years for every "human" year, I have to figure a radio ages at least 3 or 4 times as fast as we do.
That would make it 120 to 160 'human' years old.
The difference is that you can replace parts on a 1966 radio.
How long that list will be is determined BOTH by the 'mileage' and the age.
If it was stored wrapped in plastic, in a climate-controlled museum vault, it might still work. Or might not.
The 'showroom new' radio will run for no more than a week or three at best, even if it performs out of the box. After that many hours of heat and stress, the elctrolytic capacitors will begin to "remember" how old they really are, and start to fail one by one.
Every electrolytic capacitor will have to be replaced. They just don't last that long.
Too bad it doesn't have an odometer like a car. Might make it easier to judge wear and tear issues.
The relay will need its contact points cleaned. If it's worn from use, replacing it is a pain. JUST DON'T USE ANY KIND OF ABRASIVE ON IT. A strip of paper soaked in solvent, even just rubbing alcohol, will remove tarnish without removing precious metal plating on the contacts' surfaces. Fish the paper strip under the points, and draw it back out with modest finger pressure holding the gap closed, so the paper rubs against the contacts' surfaces.
Tubes are a big question mark. A good tube tester is good for weeding out the ones that are REALLY no good. Tubes that check okay on a tester may still have funny noises, or 'crackle' noises coming from them in the radio. Our routine method is to 'tap' each tube with a fingertip, while running the receiver with a weak signal on it to check for this kind of defective tube. Likewise, the same "tap" test is applied to the transmit tubes, with the radio keyed, watching for noise on a 'scope screen. Even if the tester said a tube is okay, the radio is the final authority. If that tube misbehaves in the radio, it has to be replaced.
Crystals will go bad from use. A quartz crystal is a moving part on the inside. After so many thousand hours, they just drift off frequency, and eventually fail.
Sometimes they go bad from age alone. Used to be you could guess the radio owner's home channel by which crystals were farthest off frequency.
But here's how the hit parade lines up, in order of likeliest-to-fail.
1) ALL the electrolytic caps. This is a guarantee, not a guess.
2) SOME of the tubes, maybe. The tester is your first, but not the only way to get a handle on how many are still good, and how many just aren't any more. If the sockets are dirty or tarnished, a "CONTACT" cleaner, the type that leaves NO residue may help the tube sockets. Just scrubbing the tubes' pins with generic ammonia-based window cleaner and plastic brush will tend to remove any gunk on the tubes themselves. Works particularly well for tobacco tar. Just rinse thouroughly and dry.
3) Noisy controls. Every rotary control, including the channel selector, will no doubt be noisy or intermittent. A good-quality "CONTROL"-type cleaner with a lubricant (silicone is best) is what you need. A NON-RESIDUE "CONTACT" cleaner is not the same thing. If it removes the lubrication from sliding contacts in a volume control or channel selector, they wear out from the friction.
4) The transmit-receive relay. Might be okay. Might not.
5) Worn-out, drifted or dead quartz crystals. Pretty sure that radio has 14 of them in it.
6) The built-in loudspeaker may be okay, but it's made from paper and cardboard. Even if it was stored in an unheated garage or attic for only a day, moisture will warp the speaker cone, and you'll need a new one. Or an external speaker.
And if it was wrapped in plastic, with 5000 original miles, some control cleaner and ALL the electrolytic caps might be all you need. If it wasn't stored that well, the amount of crud you need to remove is a big influence.
Or you could decide you want to restore a 1965 car. A modest, low-cost model like the Ford Mustang, say?
You'll find that the balance of "age" and "mileage" issues will be longer, and pretty different. But the basic idea is very much the same. This radio is too old for a simple "repair" job to get it back on the air for day-to-day use. After 40 years, it's going to be a "restore" job, whatever the mileage.
Oh, and just one more discouraging word. This radio has NO noise blanker, JUST and Automatic Noise Limiter (ANL) in it.
If you are now using a base radio with a blanker, switch OFF the "NB" on this radio. If your local noise level is high enough, you will no longer hear weak stations that the blanker will "pull out" from the noise.
If your local noise level isn't too bad, you'll hear okay on a working CAM-88. If the blanker made a big difference when you turned it off, that's a hint how many weak stations the CAM won't be able to hear.
73