Thanks for the photo, now I can go hunting.Well I found us a picture:
View attachment 1383027
It seems that, despite their evident superiority to any other known whetstone in the world, production at Mudgee lasted less than two years.
Page 44 here: http://lastsidepublishing.co.nz/assets/ShearingMag/2020-nov-shearingmag.pdf