(Below are notes I received that I include for the convenience of fellow researchers. You should check the DAR website as I have no affiliation with DAR.

DAR Library DAR research by mail ALL NUMBERS ARE (202) 879-3XXX
1) DAR LIBRARY: (202) 879-3XXX  229, 228, 250, 287
The DAR Library will tell you IF they have the information listed. They will tell you what the fees are for photocopying loose pages, files, book references or indexes, etc. (They are VERY busy during the month of April because of the National DAR Continental Congress Meeting, try to schedule requests at other times)

Office of Organizing Secretary General:  (202) 879-3XXX 224, 212, 325
This office has the MEMBERSHIP file.  If you have a NAME they can tell you if that person is/was a member (You should give ALL possible names [maiden, married, or more than one marriage] and ALSO if living or deceased).  IF the person was a member they can tell you the DAR National Number .. starting with #1 in 1890 and up to the #7xxxxxs today.

Office of the Registrar General (clerical): (202) 879-3XXX 247, 251
This office has two files: MEMBERSHIP BY NATIONAL NUMBER and the ANCESTOR FILE. The Membership by National Number file is numerical from #1 through present #7xxxxxs. On each card is listed the name and chapter of the member and the date admitted to DAR. On the reverse is listed her original ancestor and any other supplemental ancestors she may have proven. They might tell you the info on the back of the membership file card.

2) SEIMES MICROFILM CENTER: (202) 879-3XXX 246,245   can tell you if what you are seeking is available on microfilm/fiche. They   have applications on microfilm on any ancestor. You must first  get the number of the application.  Then pull the film.  Copies are $5 each. More recent applications for membership may be viewed in the Microfilm/fiche center. The PROOF sent in with these is microfilmed for the use of the staff genealogists only...but at a future date will be released to the public.

3) Ancestor Files of many patriots (not all) at the DAR Library. The Ancestor File contains a card with the name of the ancestor, birth and death dates and residence during the Revolution (if known), service, rank and the name(s) of spouse(s). It lists the National Numbers (no names) of members that have joined on this ancestor's service AND the child through which they joined and the spouse of the child.  At the top of the card there MAY be a notation that "data is in # national number. This is ALL the information that is on these cards. The office does NOT have the application papers..these are stored in the vault. For copies of application papers you may ask them to search the ancestor file to see if the child (through which you are descended) is listed. You may send $5 (check payable to the Treasurer General) to this office and ask for a copy of that paper.   Researchers may see these files and make copies. The documentation files on patriots accepted before 1950 (if they are extant) are available  (More current data is reserved because of invasion of privacy concerns) These ancestor files are unique. They are in physical file cases in the DAR Library.  Since the DAR Library now does research for a fee,  contact them to find out the to how much they charge for research and how much for just photocopying the information in the file. 

What these files contain are sometimes reams of info and sometimes just one or two pages on the particular name. Most of this data comes from documentation that was sent in with the original application for membership by a DAR member.  Occasional family information pages [originals] were ripped out of a family bible to prove vital statistics! Sent perhaps 100 years ago before photocopying or even good photography). Sometimes there are records donated by families settling estates who had no idea where to send   genealogical info accumulated by the deceased.

4) DAR Magazine 4 time each year publishes corrections.

5)  Lineage Research Committee of DAR  works to help prospective members who are having problems joining on a relative's application.

If someone wished to join DAR, ask for the MOST RECENT appliation on a ancestor and if  a family memberever belonged to DAR,  request a copy of that one.  Compare the two and update where necessary.  If there are errors, submit the correct information.

6) DAR NSDAR Volunteer Genealogists Committee errors or additions go to the office of the Corrections Genealogist. Previous papers that have been verified are never changed.   These are archived and microfilmed . AT THE TIME THEY WERE VERIFIED THEY WERE AS CORRECT AS WAS POSSIBLE TO ASCERTAIN. This is true for members who joined on patriots, once accepted that have since turned out to be non-patriots..or even tories...(members are not disbarred if errors are later discovered in their applications.) The ancestor card is merely flagged "error"to notify future applicants. (A code on the card indicates what sort of error and refers to documented information that was sent in later)DAR does make correction on applications as they are submitted. If additional information is available, it is added to the application at the time of verification.  However, they do not go back and make corrections to old applications.  However, the new ones are the most correct on each ancestor.  DAR over time has become  more strict about documentation. Many early papers had little or no documentation and many lines were established in error. These mailed in corrections are filed under the ancestors name in a drawer. HOWEVER THE ANCESTOR CARD IS FLAGGED. The corrections STAY in the drawer until another application on that ancestor arrives.   At THAT time the corrections are made to this new paper...thereby activating changes to the ancestor file on the in-house data base and on the official ancestor card.