http://www.smokersforums.co.uk/showthread.php?t=92971
My own guess is exactly like this expressed in post by Art_A
BTW: is the signature at your Lancasters like the one published here ? http://www.pipephil.eu/logos/en/logo-l1.html
Once I was told that such Lancaster was somehow connected with William Demuth. We know that many tobacco shops have been offering pipes signed by their names - like The Owl, british Fred Tranter in Bath, Astley's of London, etc. But maybe such pipes were also offered under other names, too ?
My guess would be a house pipe brand by Demuth's in Lancaster, Pennsylvania, America's oldest pipe shop. I visited them about 7 years ago while on a genealogy expedition, but can't remember if they had a house brand pipe named Lancaster.