Al Yellon created Bleed Cubbie Blue and has been its managing editor since 2005. He's also written three books about the Cubs, the latest is "Chicago Cubs Firsts."
As usual, let me show you the photo in a somewhat bigger size than above:
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The first clue is the team flags flying above the scoreboard. There are six on each side. Thus this would have to be before 1994, when the league split into three divisions and three sets of flags flew above the board.
A closer look, though, shows that all the flags all appear to be the same color.