UNFORTUNATELY THIS ISN'T THE WORLD FAMOUS BRITISH BUTNER SELF ADJUSTING PIPE REAMER BUT IS THE SAME DESIGN AND THE QUALITY IS BETTER THAN MOST SUBSTITUTES WE HAVE COME ACROSS.
Unfortunately as you may already be aware the British Butner pipe reamer was discontinued many years ago. We have eventually come across a reasonable substitute. They are made of highly polished steel and come packaged in a fitted black box.
INSTRUCTIONS FOR CORRECT USE: (Original British Buttner instructions)
Do not allow your pipe to become so badly carbonated as to prevent insertion of the reamer into the bowl.
Remember that an excessively carbonated pipe can be brittle and must therefore be reamed with due care.