Silver
I can't tell you of my experience with SOTO OW Explorer fares but what I can say is that when the fare first came out the fare rules (printed out for me by Canadian from their CRS) specifically excluded USA and Canada from the rule requiring the higher of the two fares (country of purcase or country of origin of first flight) to be charged. Whether this exception still exists I don't know - you'd need to get an up to date copy of the rules ex-North America