I have no doubts about my methods but of course I cannot guarantee the truth of all sources I've encountered. I have read in numerous threads and tobacco reviews that Sail was discontinued.
One of the more authentic looking sources I saw:
https://www.pipesandcigars.com/shop/end-of-an-era/1800839/?v=5000
This thread references a P&C catalog which was likely based upon the same information.
http://pipesmagazine.com/forums/topic/what-is-up-with-dutch-cavendish
Perhaps the line was just reduced as I see there are only 2 blends listed now and Sail Natural is nowhere to be found. They could also be selling old stock. I really can't say for sure without contacting the company.
As you can see from the link below, Colts were also made by STG in Canada - I believe Colts and Old Port were the leading mini tipped cigars besides Captain Black. So there is a good reason for the similarities!
https://www.st-group.com/en/careers/our-locations/canada#start
"The Canadian company offers a portfolio of cigar brands comprising Colts, Old Port, CAO, Café Crème and White Owl, as well as the Old Port, Sail and Erinmore pipe tobacco brands.
STG Canada was previously called Old Port & Colts Cigar Company. Scandinavian Tobacco Group acquired the Canadian business in 2000 when Imperial Tobacco Canada sold off its cigar activities."
To be honest, I didn't inquire any further after I saw Sail removed from my online retailer of choice and the reviews showing Sail Natural being discontinued so it could have been a mistake on my part to say they were gone.
Regardless of Sail's status, I don't think anyone will find many sources for Old Port tobacco in the US.