CSA 6P5, Plate Proof on wove, single signed Robson Lowe. The proof has a yellow cast compared to the regular issues, but is most difficult to determine without a reference copy. The only recorded sheet was found by Robson Lowe in October 1976 in the De La Rue & Co. archives in London. Lowe bought the sheet and submitted it to the Philatelic Foundation and received certificate 57 584. He signed the back of each block and they were cut into blocks and singles over the years. Some singles have signatures of Leonard H. Hartmann or PA Kaufmann, but only if they were part of a block with Lowe’s signature. CCV $150. Ex Ralph Swap. $170.