Surname Koster-Seidl (Koster-Seidl 
) , in all the world, is an extremely rare last name. The last name Koster-Seidl is characteristic of Western Europe, particularly Germany, where it is an extremely rare surname. Parts of the name also exists independently as a last name Koster, and a last name Seidl.
| VARIANT | COUNTRY |
|---|---|
| Koster-Seidl | Germany |