Decade : 1960s

The 1960s feature a bunch of seemingly experimental designs from Topps - between the first fully horizontal set in 1963-64, the first "tall boy" set in 1964-65, and the iconic TV set design in 1966-67 (shamelessly stolen from 1955 Bowman baseball), there was a lot of new ground for them in this decade.
 
Late in the 1960s marked the first time both Topps and O-Pee-Chee produced sets for the same year. In both 1968-69 and 1969-70 the two companies shared the same design, but of course the Topps set only had English on the backs, and had a smaller card count as well. O-Pee-Chee cards were traditionally produced in lower quantities overall for the north-of-the-border market, even though at any point in the last 100 years there were arguably more hockey fans in Canada than in the USA. The net result is that the O-Pee-Chee equivalents are harder to find in the same or better condition.
 
The 1968-69 sets haven't been documented yet; I'll get to those soon.