37 C.F.R. 1.176 Examination of reissue.

1. (a) A reissue application will be examined in the same manner as a non-reissue, non-provisional application, and will be subject to all the requirements of the rules related to non-reissue applications. Applications for reissue will be acted on by the examiner in advance of other applications.
2. (b) Restriction between subject matter of the original patent claims and previously unclaimed subject matter may be required (restriction involving only subject matter of the original patent claims will not be required). If restriction is required, the subject matter of the original patent claims will be held to be constructively elected unless a disclaimer of all the patent claims is filed in the reissue application, which disclaimer cannot be withdrawn by applicant.

37 CFR 1.176 provides that an original claim, if re-presented in a reissue application, will be fully examined in the same manner, and subject to the same rules as if being presented for the first time in an original non-reissue, nonprovisional application, except that division will not be required by the examiner. See MPEP § 1450 and § 1451. Reissue applications are normally examined by the same examiner who issued the patent for which reissue is requested. In addition, the application will be examined with respect to compliance with 37 CFR 1.171 -1.178 relating specifically to reissue applications, for example, the reissue oath or declaration will be carefully reviewed for compliance with 37 CFR 1.175. See MPEP § 1444 for handling applications in which the oath or declaration lacks compliance with 37 CFR 1.175. Reissue applications with related litigation will be acted on by the examiner before any other special applications, and will be acted on immediately by the examiner, subject only to a 2-month delay after publication for examining reissue applications; see MPEP § 1441.

The original patent file wrapper /file history should always be obtained and reviewed when examining a reissue application thereof.