According to U.P.U. regulations, mail franked with the stamps of the home ports of ships can be posted by the appropriate officer of that ship at a foreign port of call with those stamps being accepted as valid for postage. Since canals give ocean-going vessels access to ports along the St. Lawrence and Great Lakes system, paquebot cancellations can be found from post offices along the way from Quebec City to Port Arthur and Fort William.

Paquebot cover with a "reasonably scarce" Massena, New York "St. Lawrence Seaway / Paquebot /
First Week of Service" handstamp with a May 20, 1962 Massena, New York "Pray for Peace" slogan
cancellation franked with a 5 cent Canadian Red River Settlement commemorative issued May 3, 1962.