The 1967-68 Topps hockey set dealt with the NHL's expansion from 6 to 12 teams in a unique way: they completely ignored it.
Since sets were typically released in November, early in the hockey season, it's intended to reflect that current season, not the previous one. Any off-season transactions would usually be reflected by including the player with their new team (even when the pic frequently shows their old uni). So when the cards hit the shops, the first season as a 12-team league was well underway, and one might expect the set to reflect this new era.
But since Topps apparently didn't have the ability, capacity, time, or budget to get photos of the expansion teams' players in their new uniforms, and I guess they thought that it would look too bad to show half the players in their old unis or badly airbrushed, they ultimately decided that if they couldn't do it well, they wouldn't do it at all, and as far as they were concerned, the six new teams... just didn't exist.
Maybe they could've had six cards with team photos, maybe a single card with the six new franchises' logos, or some kind of reference that the league had doubled in size. But nothing. No mention of the new teams at all.
So if a player started the season on an expansion team, they simply weren't included in that year's set. Future HOF'ers and stars like Bob Baun (Seals), Glenn Hall (Blues), Terry Sawchuk (Kings), Andy Bathgate (Penguins) etc had no card that year. It was like they disappeared.
The only exception was Jean-Guy Talbot, who started the year with the North Stars, but was dealt to Detroit early enough in the season that Topps included him with the Red Wings.
With a lot of 2nd/3rd line players on the previous year's roster now 1st and 2nd line players on teams that Topps excluded, many players got more ice time with the Original Six and finally got immortalized on cardboard.
The set contained a whopping 24 rookie cards (up from 9 the previous year); 21% of the players in the set were making their debuts, most notably Rogie Vachon, Derek Sanderson, Jacques Lemaire, Wayne Maki, Dave Dryden, Carol Vadnais, and Glen Sather.
Averaging nineteen player cards per team, this was the last year that Topps's 132 card sets could cover most of the regular players and promising rookies (It was also the last year before the Topps/OPC split). Over the next several years, Topps would face a number of challenges trying to cram twelve, and later fourteen, teams into a 132-card set. But that's another story!
