I understand sir. You and many collectors like you concentrate on supply, and assume demand. I am just saying "demand" is not fixed in stone like many suppose. "Demand" for "key" dates only is real if there are a lot more people actively trying to assemble the "set". Maybe there are more than I realize, with registry sets, etc, trying to assemble these sets. I simply do not see them much anymore. Most collectors I see are collecting modern coins or a specialty, not something as common as buffalo nickel sets, or mercury dimes. That is why I worry "keys" for sets like this will eventually lose their base support. I view most "keys" like this today as massively overvalued versus real rarity. They only reason they haven't crashed is collectively we convinced ourselves of their value. Tons of collectors I have met only concentrate on collecting "keys", thinking somehow these are superior coins. What happens when some of these "keys" hit the market and no one wants to buy them for their sets? Will others continue to pay that money because of this group delusion that they are somehow superior? Like I said, look at harder sets to assemble. They have MUCH rarer "keys" and much lower price versus common examples. The base value of a "key" is how many people want to assemble a set. With few set collectors active, "keys" have little premium. Have almost no people pursuing a mercury dime collection, and a 1916d in VG might be worth $80. That would be in line with its rarity.
Rare is always Rare. I don't think there is any series that is recession proof, but your rare coins will be more liquid and retain more of their value in recession.
Demand changes with each net additional collector. And the population is growing, and numismatics is as accessible on the Internet as anything else. I remain bullish. In the long term. In the short term you're on your own.
Yes, but you are making huge assumptions. Just because population is growing does not mean coin collectors will. If you assume coin collectors grow, it does not mean they will collect what you and I collect. Even if they collect what you and I collect does not mean they will collect it the same way. My only advice would be advice a long time dealer gave to me years ago. "What you really want to collect is what dealers generally do not have", and that would be scarce, problem free, attractive coins. Look at what is typically in dealer trays at shows, modern coins, problem coins, common morgans and other common coins. How many problem free attractive bust quarters do you usually see? How many problem free early cents? How many nice uncleaned XF/AU barber halves? They don't have to be keys, (but can be, I am just pointing out a danger many overlook earlier about keys), but just NICE COINS, genuinely scarce, and very collectible. How the dealer explained it to me was, "I have 20 collectors who will buy that coin in a heartbeat. That is why they are never in my inventory, and this built up demand is why they will almost never go down. They are supported by collectors who wish to collect, not speculators who come and go." Yes, many times you will have to pay above "greysheet" for such things, but in my experience it is money well spent long term.
That's why I shaded my specific advice to the OP towards issues which have appeal to the "collector" whom most numismatic purists would consider an "investor." In an economic downturn, these are usually the only fish biting. Doesn't matter what happens in terms of true collectors. A huge new Upper Middle Class is burgeoning in China, and India is going to follow very soon. These will be cosmopolitan English-speakers who understand how the world works, and some of them will want investment positions in precious metals. Doesn't have to be more than a miniscule percentage when you consider the size of the pool.
In response to what I've "bolded and underlined", the funny thing is, I really don't focus on key dates. I was just responding to the OP's question. My comments were pure hypothesis. There's no way to predict with absolute certainty which coins will hold their value.
And I own a few US keys. I was simply posting my thoughts on a subject I don't think collectors think about. I understand to think about, when keys have gone up so well over 50 years, to not believe they will continue to forever. Anyway, I thought It was a constructive discussion, and hope you thought so as well.