These are "phantom" tickets as obviously the Brewers didn't make the World Series in 1988.

Phantom tickets are printed ahead so when the team wins the playoffs the tickets are ready to sell immediately after the deciding game.

As in this case when the team doesn't win the tickets are typically destroyed.  Apparently some leaked out and thus we have these available to you.

The tickets look nice at a glance but they do have some bends, creases, they are not mint.