Bidspirit auction | Worldwide Air Post Stamps and

Worldwide Air Post Stamps and Postal History - Canada - 1932, blue surcharge ''OTTAWA CONFERENCE'' 6(c) on Mercury 5c olive brown, left sheet margin block of six (2x3) with reversed ''1'' on the middle row of the edge, full OG, NH, fine, Unitrade C.v. CAD$900, Est. $300-$400 , Scott #C5