1920-21 Dunhill Ao INNER TUBE PATENTED

This is a really old Dunhill pipe.
Ao DYNHILL LONDON
MADE IN ENGLAND INNER TUBE 47 PATENDED MARCH-9-15
IT HAS NO YEAR SURFIX, SO IT IS ESTIMATED PRIOR 1921 last photograph is not from this pipe, but from pipephil website. HAS MARKS OF USE ON STEM AND MOUTHPIECE.
Thank you