Agree it looks like a three letter abbreviation, and can't think of another that would have similar pen strokes...
Being so very soon after the game played on the 18th Oct between the two sides, could there have been a disagreement of some sort over the result of that meeting and so a follow up was scheduled to settle matters?
But as the result also so heavily favored the Athletics the original score was simply unchanged...
Seems odd to have an exhibition directly after the end of the season, with the amount of baseball already watched by the supporters of both teams....?