Actually OBTP is known Oregon Board of Tax Practitioners. Get more info visit https://www.oregon.gov/obtp/Pages/index.aspx
There is also no entry point for that number either. Many states are beginning to operate tax preparers. So far, NY and OR are the only one that gives exemption and the only one that has specific entries in the Setting> Options > Preparers. From clicking F! in that area we get:
"You can modify information about your preparers, and in turn, sort mailing labels, status reports, and client lists by preparer. You should enter information for all the preparers in your firm because many program features, such as the Appointment Manager and Database Reports, use this information.

Type the preparer's name, telephone number, e-mail address, and Social Security Number.

Select the Self-Employed check box if the preparer is self-employed. If the preparer is self-employed, you must enter the preparer's SSN or PTIN.

Type the preparer's assigned Preparer Tax Identification Number in the PTIN box. You must enter the PTIN if the preparer is self-employed and you do not enter a SSN.

In the ERO PIN box, type a five digit number for this preparer, if you will be filing paperless returns. The PIN can be any five numbers. This number will be used in place of the ERO signature on Form 8453. This PIN will be used for all e-file clients assigned to this preparer.

(1040 Only) To designate the preparer(s) as a Third Party Designee, type a five-digit self-selected PIN in the Designee PIN, If Different box. A Third Party Designee is a preparer other than the person who is actually preparing the return with whom the IRS can discuss a tax return. The program uses the PIN entered here in conjunction with Designee, If Different in Client Information. This PIN only prints on main forms if you specify that Designee/IRS Discussions are allowed and the designee indicated in Client Information is someone other than the preparer of the tax return.

If the preparer has a particular certification or you want to designate a type of preparer, in the Designation list, you can choose from: Certified Public Accountant, Enrolled Agent, Unenrolled Return Preparer, Attorney, Officer, Full-Time Employee, Family Member, Enrolled Actuary, Student Attorney, Student CPA, or Enrolled Retirement Plan Agent.

Type the preparer's assigned jurisdiction or enrollment number in the Jurisdiction/Enrollment box.

Type the preparer's assigned CAF number in the CAF Number box.

Use the License # (OR Only) box only if you are preparing tax returns in Oregon. Type the license number assigned to the preparer.

Enter your New York Tax Preparer Registration Number (NYTPRIN) if preparing New York Returns. Enter "N/A" if you prepare New York returns but are not required to have this number. Beginning with the 2009 tax year, certain preparers are required to register (each year) with the NY Department of Taxation and Finance. After registration is complete, you should receive your NYTPRIN. For information about who is affected and how to register, visit the New York Web site by clicking here.

In Reference # (1040), enter the 1040 waiver reference number if the preparer received an undue hardship waiver for the calendar year in which the return is being filed.

In Letter Date (1040), enter the 1040 date of the approval from the waiver letter if the preparer received an undue hardship waiver for the calendar year in which the return is being filed.

In Reference # (1041), enter the 1041 waiver reference number if the preparer received an undue hardship waiver for the calendar year in which the return is being filed.

In Letter Date (1041), enter the 1041 date of the approval from the waiver letter if the preparer received an undue hardship waiver for the calendar year in which the return is being filed.

Click OK to save the preparer's information.

Click Cancel to not save the preparer's information."

Answers are easy. Questions are hard!