The $500 was a carry-over from the Dominion of Canada issues, a denomination for bank transfers rather than wallets, and 1935 was the only year the Bank of Canada ever printed one. The count stopped at 20,900 in English, and then the redemption machine did its work: the 1937 bilingual series arrived two years later, the old notes were recalled, and five hundred dollars was far too much money in Depression-era Canada to leave in a drawer for sentiment. Published references put the known survivors at roughly a dozen.
That arithmetic makes this the key to the entire issue, and the market prices it accordingly: an October 2014 Torex sale saw a PMG VF-25 example bring $97,750 CAD. At those numbers the certification rule is not advice, it is the transaction itself - no serious buyer or seller moves one of these outside a PMG or BCS holder.
A note that was never meant for people, hunted by everyone. The dozen-survivor estimate deserves respect on both sides of a deal: it means every genuine example is traceable in the auction record, and a fresh discovery with no history is a claim that requires extraordinary proof.
Mintage figures: United States Mint (Annual Report of the Director of the Mint), Royal Canadian Mint records, and — for the 1935 banknote issue — Bank of Canada printage records as published in the Charlton Standard Catalogue of Canadian Government Paper Money, cross-checked across independent published references. Specifications: United States Mint coin specifications.