General Precancel Info:
- Early Use and Approbation of Precancels in the U.S. Postal System – How it all started
- Precancel Device Manufacturers – History of the contracts in producing devices
- Hand Electros – 25 Years of Precancel History
- Precancel Mounting – How to NOT do it
- Don’t Apologize for Precancels – In praise of precancel collecting
- By George! – George Lupien articles on distinguishing difficult precancel types
- Chicago Super Types – Helpful article describing the differences of these difficult types
Bureau Precancel Info:
- Development of the Bureau Precancel – The story of the start of bureaus
- The Kansas City Perf. 11 x 11 – Identifying these issues
- Bureau Look-a-Likes – Local types that look similar to Bureau types, and how to tell them apart
Dated Precancel Info:
- The “First” Dated Precancel
- July 1938 Dated Checklist
- Sears, Roebuck and Company – Basics on dateds from this prolific user of precancels