Let's be honest here. First, if the owner has absolutely no intention whatsoever of selling the deck, then its worth is irrelevant. I might even go so far as to say that it is a zero worth item since it will not be sold or traded. Monetary worth (whether for buying/selling or insurance purposes) is one thing. SENTIMENTAL value is another. And the latter is next to impossible to quantify in terms of money. So to that degree, arguing over whether it should be taken out of the box and used or else left there never to be touched by human hands is kind of a moot point.
Which takes me to the next issue that someone already touched upon (so to speak). A high fidelity audio component-such as a reel to reel isn't necessarily most desireable being literally new in box.
Before the owner gets New Old Stock dollar sign greed and does something stupid, let's just point something out here. If he decides to sell it straight in the box and takes some buyer to the cleaners, he could end up with a little more than he wanted in the form of a very PO'd and very angry buyer (buyer beware issues aside for a moment here). And likewise, he could find his wide eyes and soaring elation brought back to earth REAL quick if he decides to plug it in.
As was mentioned, because of the presence of belts, oil and lubrication, and so forth, short of finding a radio station throwaway, such a find (again we're not talking sentimental or 'foaming at the mouth' value here) can actually be the worst possible thing to come across.
As we all know, these decks are twenty, maybe even thirty years old. And have never been taken out of their original containers-let alone plugged in and ran? What kind of condition do you think the belt(s) are in after remaining in an idle and fixed position since the Carter Administration? The oil, I'm sure withered away aeons ago. And being that they've never been activated, how are the curcuit boards and various transistors and such?
A NIB deck might be pretty to look at. Few would deny that. But chances are, the real worth would end there. Chances are the deck will need at least some kind of service (if not an outright overhaul) before it could be used. I'm not saying that WILL be the case here. Who knows, maybe the deck will perform to spec right out of the box after all this time. That would indeed be nothing short of striking gold. But I wouldn't bet on it, no matter what make and model the machine.
Having to rebuild a never used deck?
What kind of treasure is that?
In my humble tiny brained opinion. Nowadays, the best deck you could hope to find is not one that's been sitting in Public Storage (through umpteem cycles of summer/winter) for three decades. The best deck you can find is one that was babied and used sparingly since new in someones den or 'studio room'. A deck that's been active, but in full 'health' (that could've and should've been maintained as needed all along) is the way to go.
Just my two cents.
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DL-Which tastes better? Gravel or shoe leather?