The postcards I believe you have are not issued by the Post office. They might be G Cachets. the cachet made by the Gateway Stamp company. The cachet can be Identified by a "G" with an arch over the top located at the bottom center area.
A Cachet is a design or inscription on an envelope to commemorate a postal or philatelic event. A collectible Baseball Cachet could include a players achievements, milestone, and record breaking accomplishments. A postal stamp and cancellation will coincide in date, or and relationship to commemorate the days event. Popular Cachets include Z Silk Cachets, and Gateway G silk Cachets. Cachets are also a popular item for players to sign.
The Earthquake G - Cachet dated Oct. 17, 1989 San Francisco Calif. Earthquake artwork, autographed by Manager Roger Craig is worth about $15. and unsigned about $7.50
The Game 3 G - Cachet dated Oct. 27, 1989 San Francisco Calif. Dave Stewrart cover, autographed by Stewart is worth $20., and unsigned $7.50
There were also 4 - San Francisco - Oakland series Cachets made by Z silk -Cachet that are worth about $20. Game 3 reads canceled by Eartquake below the silk artwork.
Part of the postal cancellation stamp reads Battle of the bay (Satiation) with the Official 1989 World Series logo
1989 World Series - 1989 was released on: USA: 14 October 1989
1989 World Series - 1989 Game 1 was released on: USA: 14 October 1989
1989 World Series - 1989 Game 3 was released on: USA: 27 October 1989
1989 World Series - 1989 Game 4 was released on: USA: 28 October 1989
The Oakland Athletics beat the SF Giants in the 1989 World Series.
The Oakland Athletics beat the San Fansisco Giants in the 1989 World Series.
Material World - TV series - was created in 1989.
In 1989, The UCLA Bruins won the College World Series. They went undefeated in this series. They finished their season with a record of 48-4.
There was a 10-day delay during the 1989 World Series due to an earthquake just prior to Game 3.
1989 World Series ticket stubsA 1989 San Francisco Giants World Series full ticket played at Candlestick Park is worth about $35. - $40. and $15. - $20. for a stub. A 1989 Oakland A's World Series full ticket played at Oak-Alameda County Coliseum is worth about $125. - $150. and $25. - $50. for a stub,Condition is important. The slightest flaws could bring the price down significantly. Common flaws include; rips, creases, stains, and fading. Ticket stubs that are not ripped cleanly will also sell for less.
Earthquake
Phil Hellmuth.