CSA Catalog 6-PPa (Scott 6P5), 5¢ blue plate proof pair, positions B63-B64 from the only known sheet (since broken up), signed Robson Lowe, copy of 1976 PF Certificate for the discovery sheet by Robson Lowe. The proof has a yellow cast compared to the regular issues, but is very difficult to determine without a reference copy. CCV and SCV $150 for a single. $325.