Hawky, there were two transactions between Gallaher and Sobranie; the first, in 1968, was a sale/leaseback deal which didn’t affect the pipe tobacco business. The second, in 1980, resulted in Gallaher acquiring the remaining assets of Sobranie and moving pipe tobacco production to its own facilities in Ireland. So crudely put anything before the first half of 1980 is family (Redstone) production, anything later was made by Gallaher.
In theory there shouldn’t have been a difference; as part of the deal Gallaher received the two product manuals compiled and used by Sobranie to manufacture its tobaccos. One volume covered ingredients and proportions, the other specified processes. In practice Gallaher made changes and the blends were altered.