It is indeed a Mk2 Premier. Production was from 1975 to 1977, and though they are not as shiny as the Senior in my opinion they do handle better. If you keep a look out on that certain internet auction site, you may find some of the labels that fit in the vacant cartouche. Or maybe someone on the forum has some spares?
Its great that you're happy with it, and I think the mk2 Premier is a nice, rare, short-production model to have.
But, a dealer selling it as a Senior?? Makes me wonder if they sent the wrong gun