Kellert's Baseball Reference major league page reflects a few trades that happened while he was in the minors...
· Before 1959 Season: Sent from the Boston Red Sox to the Cincinnati Redlegs in an unknown transaction.
UNKNOWN NO MORE!
Kellert had finished the 1958 season with Minneapolis in the Red Sox organization, then was sold to the Reds and Seattle.
“The Seattle Rainiers baseball team today purchased shortstop Harry Malmberg and first baseman Frank Kellert from Minneapolis of the American Association.”
Malmberg spent a very short time in the majors, and this is a previously undocumented trade for him as well.
Back to Kellert, during the 1959 season, he went to Baltimore's AAA Miami team.
“Yesterday the club announced the purchase of first baseman Norm Zauchin and pitcher Vito Valentinetti from Washington of the American League and first baseman Frank Kellert from Seattle.”
"The club" being the Miami Marlins. The Zauchin and Valentinetti deals are previously known.
So we can close the book on the Frank Kellert Mysteries!
Kellert pic from www.tradingcarddb.com