Many of those first and last cards, like Pafko, can be very tough to find for the condition conscious collector.

Memories are precious to card collectors. Most enthusiasts can recall their very first contact with the hobby. For the majority, the introduction took place with a single, unopened and unfamiliar wax pack.

Before that package's wrapping was disturbed by the new owner, the concepts of collecting and trading cards – let alone buying and selling them were not yet relevant. The first pack is a purely sensory experience and the initial sight of the cards can be a life shaping event.

Typically, the attributes of a pack's cardboard collectible that merit instant attention are the most superficial ones. The buyer is apt to respond, right away, to the sight of a player's picture, quickly noting whether he is a famous star, a lesser figure or a total unknown. The athlete's team and its uniform are the details that are processed next (along with, perhaps, the front of the card's color scheme, franchise logo graphics and border design), and then the back of the card is examined. There, the viewer finds information that is generally presented in the form of text, statistics and the like. All of these acts of comprehension take place in merely a second or less; it's an oh so brief interval that can still be enough to ignite a long burning flame.

At some undefined point in the acquaintance making session that takes place between a card pack and its buyer the unsuspecting purchaser who may, after all, have simply wanted a piece of gum a subtle revelation occurs. The cards' new owner discovers the pieces are numbered. If it's 1962, for instance, and Stan Musial is the face greeting the fortunate person who parts the folds of the green Topps Company wrapper, it will eventually be apparent that a pair of numerals "50" sits inside a small, baseball styled circle at the cardback's upper left corner. This "50" doesn't seem to have any special significance, yet it occupies a spot that's hard to overlook. The idea dawns rather quickly that this prized Stan the Man piece is part of a sequence, and the intellect, unbidden, wishes for additional information.

If Musial was hiding inside a five cent pack (the premium size that contained more than one card), further details were close at hand, as his packmates would have carried similarly placed identifiers: "32" John Roseboro, "21" Jim Kaat, "75" Milt Pappas, and an entirely different thing here – "53," on a card that showcases Mickey Mantle, Roger Maris and the American League's other home run leaders for 1961!

Clearly, a pattern was taking shape. These numbers held designated positions in a mysterious sequence and their presence was triggering the urge to investigate further. Naturally, it's just one small step from that point – the inevitable – trying to obtain all of the numbers. The new goal was to obtain the full array of card subjects and having every one of them in hand simultaneously.

More clues became available with the purchase of additional packs. Inside one of those would likely have been the cards' Rosetta Stone, a piece that answered many questions: the Checklist ("22") for 1962 Topps' Series 1.

Among its orderly roster were numbers "1" Roger Maris, "5" Sandy Koufax, "45" Brooks Robinson, and many more, extending all the way to number 88. Eighty eight different cards soon became the brand-new hobbyist's objective, "... got to get them all," and more packs were bought with this goal in mind.

As subsequent pack buys were made and examined, a couple of new wrinkles emerged that complicated the seemingly straightforward business of assembling all of the cards. Card #22 in the 1962 Topps set is sometimes found displaying numbers 121 through 176 on its back, instead of the proper span between #33 and #88. Not only did the "Wrong Back" Checklist fail to list the issue's subjects in proper order, it gave a frustrating "sneak preview" to the novice enthusiast. No matter how many packs were opened on the heels of the Checklist's revelation, it was, at that moment, impossible to obtain "150" Al Kaline or "170" Ron Santo. They were in a series that had yet to go on sale, and it would take a while for the collector to become wise to Topps' "come on" method of promoting upcoming segments of its product.

Having stuck with it to this point, however, a buyer was usually hooked. The prospect of completing a full set of cards became a challenge and a fascination. Trading ("swapping") began to occur as would be completists tried to overcome their respective set's deficits by exchanging duplicates. Before long, the avocation naturally spread among individuals who discovered that they had this "set building" preoccupation in common.

A fan's passion for building sets derives from the systematic behavior of looking for a multitude of numbers and placing them in order. It is an activity that separates "collectors" from undirected gatherers or accumulators. Accordingly, a card maker's idea of placing sequential numbers on cards was perhaps the most significant development in the collecting hobby. With card numbers in place, the quest for completion is elementary. So, the compulsion of set building begins the moment a collector is first exposed to cards. Once the seed of interest is planted, the drive to nurture its growth is demonstrably insatiable!

Although the incentive to put together sets can be provoked by simple curiosity about the card numbers, motivation is sustained by results. A complete set from any era acts as a time capsule, allowing the viewer to re-experience events that were current at the time the assembly was created. Full sets enable nostalgic tours of the 1950s, thoughtful recollections of the 1960s, or more recent reminiscing about the 1970s. Revisiting an early 1960s set brings to mind that period's then new multi-player cards, its League Leaders, its Team cards and, in general, the season's activities in their most favorable light. A 1975 Topps set, with its gaudy, color edged motif, just looks like a 1970s production, and it's a delight to view. But these more contemplative satisfactions aren't immediately apparent to the person who's just bought a first pack, and they're well down the road for someone who's barely had time to notice the card numbers!

The lesson brought to bear by the 1962 Topps baseball cards ("a checklist isn't always what it seems to be") has corollaries in other years' collectibles too. Most types of cards have their own quirks that, depending upon one's point of view, make the effort to collect them especially vexing or rewarding.

For example, logic dictates that the star players in a set would be the most desirable. Although that notion is frequently true, it's just as often contradicted by exceptions. Certain entries are short printed in various issues, as press sheet layout and other considerations caused specific cards to be produced in smaller quantities than others. Production figures alone, in cases like these, mandate that cards like the 1963 Topps #470 Tom Tresh (an "SP") will be inherently tougher to find – and thus more "valuable" to a set builder – than the same year, same series depiction of Hall of Famer Orlando Cepeda (#520). The "SP" phenomenon occurs repeatedly in set collecting, as does the circumstance in which "High Numbers" (those portions of a set released near the end of a season) are made in lesser abundance than the earlier, preceding groups. No sport's or topic's cards are immune from these built-in scarcities. They are a challenge in any set building arena!

Sometimes, the manufacturer isn't to blame. In years gone by, before cards were perceived to hold actual "value," discarding duplicate "common cards" of undistinguished players was a routine part of a setbuilder's housecleaning. Years later, many of those "commons" deemed unnecessary and disposable at their time of issue are actually the same pieces hungered for by advanced collectors seeking to assemble highgrade sets.

Condition constitutes another matter of some gravity among setbuilders. If one aspires to complete a full set, doesn't it make sense that an attractive, uncirculated looking set of all the cards would be best of all? As collecting evolved and the appearance of cards became a factor in their desirability, "condition rarity" became widely understood to apply to those cards that were always a chore to find in high-grade. The first and last cards in a set, due to rubber banding and in-order stacking, are especially susceptible to damage. Number one cards like the 1952 Topps Andy Pafko, 1953 Topps Jackie Robinson and 1966 Topps Willie Mays are condition rarities, as are such last cards as the 1954 Topps #250 Ted Williams and 1967 Topps #609 Tommy John. Many of those first and last cards, like Pafko, can be very tough to find for the condition conscious collector.

Modern times have brought about sophistication in many pursuits, and so it is with trading cards and set building. These cards are much more elaborate than in past years, and the manner in which they're collected has seen dramatic improvement. Years ago, devotees of setbuilding relied on word-of-mouth, casual contact and a few dealers to gain information about set building projects and to acquire missing cards. Today, the PSA Set Registry allows precise comparison between collectors' holdings (conferring "bragging rights" at the same time) and reveals which cards are notably scarce. By studying the PSA Population Report data, participants can identify condition rarities and adjust their collecting strategies to elevate the priority of those items in the search for material.

In order to do justice to each card issue, it was necessary to select a very finite, too limited number of sets for this "All-Time" listing. They were chosen on the basis of inherent, enduring appeal and widespread appreciation that each one inspires among hobbyists. It must be noted that these 30 sets are a cultural art form's highlights, not its full extent. More than a century of trading card production has yielded numerous issues that are truly fantastic. Isolating an elite few for "All-Time" honors requires methods of necessity that leave many great sets on the sidelines.

The enjoyment realized from completing sets of cards is evident to anyone who has tried it, and it's a definite force among those who have succeeded. Finishing a year's worth of cards entitles the hobbyist to look over a gallery in full bloom, with stars and memorable commons displayed together in a neat, inclusive continuum. It's fun to collect single cards, but there's closure in sets and satisfactory completion is often regarded as a beginning, rather than an end, with a hobbyist preparing for their next collecting challenge.