Surname Koestoer (Koestoer 
) , around the globe, is a rare cognomen. The surname Koestoer is habitual in Indonesia, where it is a rare surname, and the United States, where it is an extremely rare surname.
| VARIANT | COUNTRY |
|---|---|
| Koestoer | Indonesia, United States |
| raldi artono koestoer ID (b. 1954) |
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| raldi hendro toro seputro koestoer ID |
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