Cool,Was just talking about Ashton sizes yesterday at club meetup.
I've got a XX coming, and according to its measurements it could easily be a XXX.
Like the Dunhill group numbers, it varies wildly - sometimes nonsensically.
This early X has a chamber size I've seen on Dunhill groups 1, 2, and 3 - about .73 x 1.5".
Depending on the tobacco cut, this pipe usually lasts me 40-60 minutes.
I have a 2 and love it. I have 3’s, LX and ElX as well but no X as of yet.
Your X is a great looking pipe and grain.