Obviously aside from the used 12 pence Queen Victoria, the real major stumbling block to finishing Canada is the 1868 2 cent green “Large Queen” on laid paper of which only 3 used examples are recorded.  If you are tackling Canada mint, for our money pride of place goes to 1899 “Port Hood” bisect overprint provisionals.  By our estimation not more than 5 mint sets exist, of which we have handled 3.  The rest of the basic numbers of Canada are easy enough to do.