The Reexamination Certificates File contains a listing of all Reexamination Certificates for US patent documents and lists the following fields:
Kind of Document Code (B1, B2, C1, C2, F1 and F2)
The Reexamination Certificate File is normally updated on a monthly basis.
In addition, layout information for the Reexamination Certificates File is provided. Additional information regarding Reexamination Certificates can be found on the list at the following location: http://www.uspto.gov/patents/process/search/authority/reexam/index.jsp.