[Ger-Poland-Volhynia] Born in Topcza/Toptscha 1903

[Javier Acosta]

Maybe someone could help me, my wife's grandmother Agathe Buss was born
in Topcza/Toptscha  near Korets,Rowno on 2/12/1903, the question is was she polish or russian at that time ?
Are there any registers of birth from Toptscha, Rowno ? Where can we find them? Are there in Shitomir archives nowadays?
When she migrated to Argentina with her husband Adolf Kuhn and two children in 1926 , 
when they arrived the records I found say that they were Polish Citizens, but we never found their passports
or other documents.

The only clue we found is a paper manuscript saying that he had an " identity document number 7 given to Adolf Kuhn on 1/13/1926 in Rowne"
I think that number 7 weird for a Passport. What kind of documents the authorities gave to the travelers in Rowne at that time ?
They arrived in Buenos Aires, Argentina on 2/1/1926, later in 1928 they moved to Paraguay.

Thanks

Javier