Phillumeny is the collecting of matchcovers...and matchboxes and labels, so you're not limited to matchcovers unless you wish to be. However, if you're seriously going to collect boxes and/or labels, there are some factors you should be aware of.
With regard to boxes, although there are plenty of U.S. boxes to be collected, their primary use remains in the Old Wolrd (Europe, Asia, and Africa). Here in North America, the primary emphasis for collectors, and the preponderance of production, is on matchcovers. Within a few decades of the invention of the matchbook (1892, here in the U.S.), the matchbook became the primary format for domestic matches. Hence, the North American interest in those over boxes.
Still, there is a plentiful supply of American boxes. As of this writing, for example, there are at least 12,750 different American Ace boxes, and 20,000 Pocketboxes...and those are just two American brands. And, much to the delight of collectors, both those brands tend to open very easily (most collectors throw the drawer away and then open the cover along the seam where the flap has been glued).
If you're going to collect foreign boxes, there are many more of them, but they also come in many different sizes (making it more difficult to mount them all in albums), and most seem to have be put together with Super Glue. Also, there is the problem of procuring such. You'll almost certainly have to develop connections to foreign collectors to act as your source. And then, there is the problem with foreign languages. How good is your Arabic, or Hindi, for example?
Personally, I've always found boxes to be a pain, although I certainly collect them when they happen to fall into my other categories.
When it comes to labels, if you're here in North America, you're in the wrong continent altogether. Labels haven't been used here in the U.S. for a very, very long time, and so, consequently, collectors here have little or no interest in collecting such, even though they're the oldest of the three types of collectibles found within the hobby of phillumeny. They still abound in the Old World, though.
But, what are labels anyway? In the old days, the design and text that were to go on the matchbox were actually printed on a label, which was then glued onto the box, itself. Collectors could then soak off the label and collect such. But, Western countries long ago moved to either printing directly on the box or on a wrapper which could not be removed from the box...hence, no more labels there. Still, Asia, Africa, and especially Eastern Europe, continue to pour forth labels in vast quantities.
Collecting labels is like collecting stamps. They're very thin pieces of paper; you need to handle them with tweezers. They need to be handled with care. And, since all but a relative few are much smaller than a matchcover, they're more difficult to keep track of.
Your only real source of labels is going to be foreign collectors...which also means foreign postage. Again, though, there's always ebay.

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