I wanted emphasize the Entry # a bit more. Yesterday and today we were discussing Subject, Policy, & Correspondence Files. These are NOT the A-Files or C-Files that the INS/USCIS provides genealogy research for. These correspondence files were turned over to NARA & are in the National Archives.
Entry#9 — INS Policy Corespondence
Entry#26 — Bureau of Naturalization Correspondence
Entry#P-4A — Central Office Files
The Subject Card Indexes in Ancestry.com are Entry#9.
These are all RG85, Entry#9. The final piece of info (File#) comes from the subject index card. In Leon Pieszczochowicz ‘s case it was: 55,874-84
So that is how I got my three pieces. Most people will be Entry#9 (deportation, illiterate, disease, crimes, etc. — immigration related) with some people possibly falling into Entry#26 if their correspondence is about the Naturalization (naturalization issues).