I wouldn't call the NH craze a "plot" but I do think there was a certain degree of "collusion" involved, meaning that once the collectibles people (silver, gold, baseball cards, Beanie Babies, toys, and so on) got ahold of stamp collecting in about the mid-1970s, all of a sudden we had the NH phenomenon. That came from somewhere, and saying it was market-driven sounds just fine for why it kept going (to make money!)--but where did it come from in the first place?
It came from a burst of enthusiasm for collectibles in the inflation-ridden '70s combined with a new (or maybe they were old) group of stamp "investment" dealers. I remember the stamp market being tracked like it was the stock market. Even Linn's Stamp News had a "Dow Jones" bar graph to show the rising prices. It got a little silly.
In an inflation-ravaged national economy, collectibles were claimed to hold their value better than stocks, bonds, and so on, and this included even Beanie Babies and new in-the-box toys, and so on. It was about money, not stamp quality. If you slather "gum" on the back of an ugly stamp, it doesn't get more attractive. The same for a beautiful stamp. You can't even see the gum when the stamp is mounted in an album. You could argue that a thin which isn't visible from the front of the stamp is the same thing, but a thin endangers the integrity of the stamp so avoiding stamps with thins makes sense. Gum, or lack of it, doesn't. In fact in some ways gum is potentially damaging to stamps. The gum can stick the stamp to the page, ruining it forever. Or the gum can crack, ruining the front of the stamp. I happens. Stamps without gum don't do that.
There's nothing "natural" about the interest in gum on the back of stamps all of a sudden. It was a demand invented by stamp speculators. It was created by people who wanted to be able to sell something at a higher price, and purchased by people who hoped to protect the value of their investments. This same thing had once been done (in the Netherlands) with tulip bulbs. That made no sense then, either. Or it made sense if you made money. But most people lost money. Will the MNH craze also disappear, leaving many collector-investors holding onto overpriced stamps? Don't know.
Imagine if a few art dealers decided to jack up the price of paintings that had never been hung before.
Dealer:
"But this work of art doesn't even have screw holes in the frame. It's never been on a wall. That's why we charge twice as much as if it had been hanging on the wall somewhere." No one would buy that logic for art. Why buy it for stamps? The origin of the MNH craze was market-driven only if you're referring to stamp speculators.
That the phenomenon continues is a little ridiculous today. Remember "slabbed" stamps? They were stamp collecting's answer to "slabbed" baseball cards, cards sealed inside plastic cases so no one could ever touch them. This was supposed to set their price higher as a protected investment, one that could not be damaged. Do collectors buy slabbed stamps? If I did, the first thing I'd do is break open the plastic and take out the stamp so it could breathe again. The investment world can get awfully silly at times.
This doesn't mean stamps aren't a good investment. Maybe they are, maybe they aren't.
But there's also another way to look at it. While the eyes of the big money collectors are on MNH (untouched, unbreathed upon . . . ) stamps in "minty" condition, for very good prices I can buy lots of excellent quality stamps with hinge marks on the back or (horror or horrors!) no gum at all. That's just fine with me. Choosing between a MNH stamp and an excellent hinged stamp, I'll go with the latter if the price is a good deal lower. I'll leave the "investing" part of collecting to others. And keep in mind that if the MNH investors do really well it may drive up the prices of stamps you'd like to buy.
Back to the original question:
- Some stamps may have been saved for postal use but never used.
- Or they were stored in glassine or regular envelopes, or a stock book, perhaps as a collector's second or third copy of a stamp.
- Or they were mounted in an album as part of a multiple or with selvage attached, with the hinge applied to one of the other stamps or the selvage.
- Some MNH classic era stamps have been regummed or "steamed" to remove the hinge mark. This further points up how silly MNH really is. I wonder if you could lick off the hinge mark? Would it make them worth twice as much if I licked the hinge marks off the back of some of my stamps?
