The same card is on Ancestry.com
The card  is explained on Ancestry:   Arrival Date is June 13, 1930. 
Another card on Ancestry indicates his naturalization took place at the Princeton Ill. Circuit Court, Bureau County Ill.


The records are not indexed on FamilySearch, but the images themselves have an alphabetical index on the first few pages 
https://www.familysearch.org/search/catalog/2820216?availability=Family%20History%20Library

Jacob Brostoff's Declaration is record #1459, image #42 in this set.
https://www.familysearch.org/ark:/61903/3:1:3Q9M-CS4S-P3V8-9?i=41&cat=2820216

His Petition is  record  #759, image #161 in this set.   This matches P-759 on the Ancestry Index card.
https://www.familysearch.org/ark:/61903/3:1:3Q9M-CS42-SQK7-F?i=160&cat=2820216


David Rosen
Boston, MA