The 1971 cards are easy to distinguish from the '70 cards because the '71s have a world series MLB logo on them. The backs are different too. The '70 cards had blue printing while the '71s are black. Though released just one year later, the '71 set has two more cards. One would be for the 1970 series. The other is for 1904. There was no 1904 series (the Giants refused to play) and the '70 set just skipped over 1904. For the 1971 set, a card explaining the lack of an '04 series was made.
Fleer updated the set throughout the 1970s, adding a card for the most recent series. That didn't affect me as a Cubs collector, since, sadly, there weren't any more Cubs series appearances.
Here are the ten Cubs cards from the 1971 World Series set.
On Wednesday I'll have the two sets side by side.